Hi everyone,
My name is ColossalAiur, as you can see, I was a Starcraft 1 player for 12 years and I just started playing LOL in Feb. 2014. I main Protoss and when I came across Xerath in the champion pool and I just feel like this guy is one of my Protoss Race. I was amazed by his super powerful Arcanopulse and Eye of Destruction, also his most famous ultimate, Rite of the Arcane. Until Today I have played Xerath in 90 percent of my normal and Ranked games and I snowball hard(Average 9.3 kills and 10.2 assist per ranked game) and die very little (3.3 on average in ranked games). As a new player in LOL, I experienced a very hard time trying to master his skillshots and getting the sense of "being safe" yet still being aware of anything that's going on across the map.

This is my first guide but I have read lots of guides on Mobafire, especially guides on Xerath. I might be talking about the same things as other guides do, but all of the contents are based on my own game experience. I have learned a lot from the other guides, and hopefully my guide will also help others when they play and write guides about Xerath.

Table of Contents:

-Pros / Cons

-Runes

-Masteries

-Summoner Spells

-Skillshots

-Items

-Laning

-Teamwork

-Pro Play videos

(Please click on the table with hyperlink to jump to chapters.)

If you need to convince yourself to trust my guide, here are my scores using Xerath:
Ranked Game Plays: 79
Wins:49
Losses:30
Recent KDA: 7.6/2.8/8.4
Recent Wins(including normal): 26
Recent Losses(including normal): 10

(Some people say that a mage with average kills of 7.6 is useless. My response to that is simple: before you get the kill, make sure you are not dying. I would rather stay in mid and farm forever in order to outscale the enemies rather than facing another 10/10/10 mid ap assassin.)

This guide is almost finished and please let me know if there is anything else you want to see.

Pros

+ Super Long Range + Good Laning + Mid Game Master + AOE AP Damage + Best Turret Sieging + Not Very Match-up Dependent

Basically everything comes from his range and AOE damage. Xerath's Arcanopulse and Eye of Destruction combo can do really good job when creeping, and he can harass the enemy in mid game with no cost but 120 mana every 5-7 seconds. Just imagine a super cannon that does 400 magic damage from 1100 units of range away to the turret bombarding any champion in range, no other champion can give higher pressure than Xerath. He also has the highest base AP burst among all AP mid champions, and his AP scaling ratios are also very good, which simply means he outscales any mid mages as the game goes on. In a word, he is superior to any other mid mages in terms of power. I will talk about match-up later on but he is not quite bad against anyone.

Cons

- Extremely Vision Dependent - Extremely Team Dependent - Extremely Skill Dependent - Extremely Mana Dependent

Xerath has his problems: immobile, crazy mana consuming, super fragile, all skillshots are not really easy to land as other champions, and a bad Xerath would feed hard if he is laning without vision(Sometimes I do that too when I think the enemy mid laner was quite far from me and the jungler like Vi or Amumu just flashes out from the bush and roots me down forever. lol).Also a good Xerath will die hard if the team does not help him because of his super immobility. But don't worry, my build will try to solve these problems as best as one can.

Offensive:

---You can also pick Expose Weakness rather than Arcane Blade . Arcane Blade will provide 2 additional magic damage to minions when last hitting, whi h is slightly more helpful in early cs.

Utility:

---If your jungler is gonna give you blue very often, take Runic Affinity rather than Culinary Master .

---Some people take movement speed rather than CDR for summoner spells. I did that like 1 month ago but now I realize how important the summoner spells are to Xerath and I would like to take that CDR. You can take movement speed, but that 3 points of masteries can only yield you 5 Movement Speed, which is not very significant.

Runes

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• 3* Greater Quintessence of Ability Power: This will give you 15, plus 8 from masteries, 23 AP when you start. Buying a doran ring will give you 39 AP.
  
• 5* Greater Mark of Hybrid Penetration+4* Greater Mark of Magic Penetration: DESCRIPTION
  
• 9* Greater Glyph of Scaling Cooldown Reduction: This might not be a good thing if you are playing against another Xerath since you guys really just poke each other and the one that does more damage wins the match-up. But if you are playing against anyone else, this should not be a really big problem.
  Let's do a simple math: Suppose we take 9* Greater Glyph of Ability Power instead of 9* Greater Glyph of Scaling Cooldown Reduction, you end up with 1.2*9=10.8 more AP. Your Q gains around 7 more damage and your W gains 6(10 in center) damage. Considering the enemy's Magic Resistance, the full combo yield you around 10 to 13 more true damage. However if we do not have any CDR in Runes and only 2.5% CDR from masteries, we would only end up with 22.5% CDR after getting Athene's Unholy Grail, and there is really no good item that can provide us enough CDR and other good stats to fit on Xerath well. This is really about personal choices about whether you want to be more powerful early or poke harder late game. I prefer the late game advantage so I pick the scaling CDR runes.
  The Result from the CDR runes is that your CDR converges to 37.5% as you are approaching lv18, and when you have a blue buff and Athene's Unholy Grail you will get 40% CDR for sure. This will make Xerath a crazy mid lane pusher and poke the enemy mid laner down ASAP. Also since you are AP mid and Chalice of Harmony provides you super nice mana regen to stay in lane, you are lving up very fast, therefore I think the 9* Greater Glyph of Scaling Cooldown Reduction will pay you off in time.
  
• 9* Greater Seal of Mana Regeneration: This is the important part. With these 9 runes together with masteries, starting mana regen and Doran Rings, your mana regen at lv1 is 16 per 5 seconds, which is very high. As you level up higher, you will find this very helpful when you trade with your enemy badly and you guys both end up with low health and low mana. However, since your mana regen is much higher, you can still poke your enemy without risking your life to the minion line for mana surging, yet making that one more poke can just get your opponent back home, or let your jungler finish it off. And when you are playing a hard match-up or you just mess up the early trades, this will probably be the case. Some people would insist on taking Greater Seal of Armor and Greater Seal of Health, but I would like that massive mana regen to keep me safe rather than 9 points of armor. (I have tried changing all 9* Greater Seal of Mana Regeneration to 9* Greater Seal of Armor or 9* Greater Seal of Health, which can increase your chance of survival in lane, but you will feel the difference whne your mana and health get low at the same time. Taking 9* Greater Seal of Mana Regeneration might be a safer choice in that situation.)
  

As you know, Xerath is very vulnerable to bruisers, assassins and unexpected ganks, therefore summoner spells are extremely helpful to help you surviving from early game aggressive plays.

• This is a must-pick spell for Xerath. It helps you dodging any incoming skillshots and dragging enemy into turret range(like Zed and Vi) which can even yield you a kill because of this. Another use of Flash is to close the gap. With your Flash available, your range of Arcanopulse is actually much longer. Charge your Arcanopulse and flash in when it almost reaches max range, then fire once you flash. You can also do this with your Eye of Destruction and Shocking Orb. This is pretty hard to master, but they really worth a try, since it is so effective and looks pretty awesome!
  
  
• Here is the reason why I take Exhaust: when I'm playing blind pick, I do not know who I am playing against until the game is loading, so I would just think about the worst case scenario: mid assassins who can snowball really hard and combo me down in 2 second, like Fizz and Zed. And I find Exhaust work even better than Flash because it significantly reduces the damage you are receiving, slows the enemy and amplifies your damage. This pick does not only fit on Xerath but any squishy mid laner who is facing burst champions like Fizz, Zed, Nidalee, Akali, Kassadin and others. This may also be a good pick against Yasuo since he has no escape but running, and Exhaust just freezes him and almost give you a secured kill when your jungler ganks.( Yasuo is so scary in late game and usually plays aggressively in lane. If your jungler does not gank him at all and stay in jungle for his farm, gg.) Also, when the enemy jungler comes to gank you, pick the target who does the most damage, and try not feeding your enemy laner. However, be aware of junglers who have some hard cc which would just make Exhaust useless. Ward hard and playing passive when you feel scared.
  Exhaust is even more scary when late game comes. Your support exhausts adc, and you exhaust the top ad bruiser like Riven and Fiora. Exhaust on ad bruisers in late game is hell because they cannot finish their task in time and escape. (I'm talking about Riven, Rengar, Kha'Zix, Fiora, Master Yi, top Vayne, top Quinn, Yasuo, Zed, ......just imagine how useful this exhaust is for your whole team) This saves both you and your adc.
  
  
• I take Heal if I am laning against mages and my adc does not take Heal. Although Heal is weaker than Barrier in terms of hp, but Heal provides bonus movement speed and heals your ally. It will help you more if your jungler comes to help you a lot and sometimes can save you guys from being double-killed. One thing to mention is that since Heal's bonus movement speed is reduced to 1 second, do not risk yourself (like face checking bush) because you have all your summoner spells in hand. You could escape with 2 second bonus movement speed, but not 1 second.
  
  
• Ghost is also a popular choice on Xerath because of these three reasons:
  1. Xerath is very immobile, and ghost fixes this to the best, and it lasts pretty long (10 seconds), which can save your life much better than Heal if enemies who are chasing you does not have hard cc to lock you down.
  2. Xerath has very long range, but sometimes it is still not enough. A Ghost can help you get into range and give them an unexpected Arcanopulse.
  3. There is a boot upgrade called Enchantment: Distortion. If you did not really pay attention, Riot has buffed it HARD recently so that people have a reason to buy it: It reduces cooldown of Flash, Teleport and Ghost by 20% and further enhances these spells. What does that mean? Once you have Distortion, enemy bruisers and assassins will feel extremely terrible when chasing you off. You have a Ghost with 40% bonus speed(which is going to be 385*1.4=539!!) every 210*0.9(from mastries)*0.8(from Enchantment: Distortion)=151.2 second, and a Flash with 30% bonus speed for 1 second and cooldown of 300*.9*.8=216 sec. Taking your Zhonya's Hourglass into account, you are one of the most difficult target for the enemy team to take down. You can almost use Ghost and Zhonya's Hourglass in every late game teamfight because the cooldowns are so low. If your enemy laner is a mid mage and you are not under very high risk when laning, take it if your adc takes Heal.
• Ignite is not a very popular spell on Xerath because his range is long and you have to get close to burn your enemy up, and it makes you less safe in lane against enemy ganks. However, it is viable in low-elo plays if you know you can dominate the lane. This is because it will get your enemy laner out of lane much faster. If you don't take Ignite, your enemy may just stay in lane and focus on dodging all your skillshots, and sometimes it is extremely annoying for you. In my opinion though I don't take Ignite because my flash+ Arcanopulse and Rite of the Arcane is quite accurate and probably will finish my enemy off.

This is the most controversial part about Xerath, as most people start playing Xerath only from end of July, 2014.(if you look at "Spectate Live", you would see Xerath showing up in one of the five games at least, which is much much more than before. Thanks to Froggen's first successful use of Xerath in LCS EU, people finally realize that Xerath can win games, especially competitive ones.) As people start playing him more, you can see lots of different paths of builds. Let's discuss them all:

• ->
  I do not like this path personally because it does not benefit Xerath at early laning phase. Tear of the Goddess does not give any AP until you upgrade it to Archangel's Staff, also Rod of Ages only provides you 60 AP with 2800 gold, without any other stats, such as CDR and Magic Penetration.
  
  Let's make comparisons between Xerath and the champions who fit well on this pair: Ryze, Karthus, Lissandra and Kassadin. Ryze fits perfect because of his passive and his speed of spending mana. Karthus builds mana stacker because he spams his Q forever and his Q and E costs lots of mana. Lissandra and Kassadin need this pair because the tankiness and mana pool they provide.(they even go off-tank if they have to!)
  
  Does Xerath have any of the needs I mentioned above? No. He does not spam that many skillshots. He does not need tankiness since his range is crazy and if you get caught by any bruiser, you are dead anyway. Also because of your passive, you have infinite mana sustain in late game. As long as your allies know about the basics of Xerath, they would just leave a minion for you to surge mana and let you poke with Arcanopulse forever. Another thing is that when the teamfight is on and you really run out of mana, you just auto-attack one enemy tank and you surge half of your mana pool. So why bother stacking mana for the whole game? Trust me, if you do well in early and mid game, you are the focus of the fight: your allies peel you, and enemy bruisers jump on you. You will always find a target to surge mana.
  
  However, what if you do not have the chance to surge mana? I would say buy the Tear of the Goddess as soon as possible. I really don't see Rod of Ages as a useful item to you but Archangel's Staff will provide you unlimited mana together with the highest AP any item can ever give you. It also has the magic shield which prevents you from getting bursted down. I need some further experiment on this but I believe it should work.
  
• vs
  As S4 goes, I dislike Athene's Unholy Grail more and more since they nerf its MR by 20 and never lower its price. This is like gifting Katarina another Abyssal Mask's aura against you without paying you anything back. However, the nerf does not affect any of its mana regen, and it could be the only reason why one could choose Athene's Unholy Grail over Morellonomicon. Athene's Unholy Grail gives you 50 percent more mana regen once you get Chalice of Harmony.(from my experience) It also gives you 15 percent of mana once you get any kill, which almost keep you away from mana problem forever.
  
  Lets talk about Morellonomicon. To be fair, lets talk about Morellonomicon+ Doran's Ring vs Athene's Unholy Grail since they have the same cost. Morellonomicon+ Doran's Ring gives you 80+15=95 AP, 20 CDR, 13 mana per 5 sec, 4 mana per minion kill, 60 health and Grievous wounds.(I don't think this passive is so useful in early or mid game as you are not facing a tank who has super high HP sustain) you get 35 more AP, a little bit less mana regen and 20 less magic resistance. This will even give you 10 more AP with Rabadon's Deathcap. But as a mid AP champion with super long range, the contributions of you to the team are damage, CC, slow. If you are not under the situation that your enemy laner is poking you hard and you really need that magic resistance to stay in lane, get more AP for your team and enjoy decisive wins on dragon!
  
  Here's some update to this pair of items: I know a lot of people prefer getting early advantage from runes, and they do not want the nine scale CDR runes. What's gonna happen is that during the late game, you have only 22.5% CDR once your blue buff is taken away by anyone. Your mana sustain will also suffer from this if you pick Morellonomicon rather than Athene's Unholy Grail. What you can do is to buy both of them. Yes buy both since they are not very expensive and have strong mana sustains, also they provide decent amount of AP. Since Athene's Unholy Grail's mana font passive stacks on Morellonomicon's mana regen, you will gain even more mana regen and fires your Arcanopulse without any limit. No matter which one you buy first, getting the second mana sustain is worthy for Xerath because of his huge demand of mana and a reletively small mana pool. However, if you are not facing a very hard lane match-up, pick the runes I suggested and scale harder late game in order to help your team.
  
• 
  I have seen guides that dislike this item because they think the active is not so useful compared to other champions who excels at single-target burst. However it gives you 120ap and 10 cdr plus that active. My opinion is that even though you are not the one who should get close and pick kills using this item, it is still very effective against enemy who makes every effort to get you, and it may work very well if your top laner is also AP.(like Ryze and Vladimir) You can adjust my rune page if you plan to take this item since it gives you additional CDR. I recommend this item in normal games because a lot of normal players are very greedy and only build full damage. Just destroy them with this item.
  
  
  
• (To Clarify, you would definitely grab this item as your first item if you plan to take it. Its aura is most effective in lane.)
  The nerf of Athene's Unholy Grail brings a big problem to all mid AP mages against mid AP assassins like Akali, Katarina, Kassadin and Fizz: where can you get more magic resistance to make sure that you do not get one shot down? Sometimes you may have to turn to Abyssal Mask for help.
  Abyssal Mask provides 70 AP and 45 magic resistance and a magic reduction aura of 20.(range 700) The reason people do not buy Abyssal Mask on Xerath because the range of that aura is small and the magic resistance from Athene's Unholy Grail is usually enough. But now these assassins can jump on you without any hesitation even if you have Athene's Unholy Grail. Since they jump on you so much now, this aura is very effective against these assassins.
  Based on the magic resistance wiki(http://leagueoflegends.wikia.com/wiki/Magic_resistance), magic resistance works by reducing magic damage with a multiplier of 100/(100+mr). Let's say we are facing a Fizz with 9* Glyph of Magic Resist, which gives it 12 flat magic resistance, and a Fizz at lv10 would have 30+1.25*10+12=54.5 magic resistance. My runes give 6.5 magic penetration, which leaves Fizz 48 magic resistance. Here's the math:
  with Abyssal Mask: 100/128=0.78125
  without Abyssal Mask: 100/148=0.6757
  Which means it increases your magic damage to Fizz by 10 percent.
  
  Also for your own resistance:
  with Abyssal Mask: 100/123=0.813
  without Abyssal Mask: 100/168=0.5952
  Which means it reduces Fizz's damage to you by 22 percent.
  
  As a result, this item reduces Fizz's damage to you by 22 percent and increases your damage to Fizz by 10 percent when it jumps on you. I believe this helps you a lot if you find Fizz playing aggressive in lane. It also works well when combined with exhaust, which just makes Fizz's combo useless, slow and weaken it.All of these would seriously keep Fizz away from you. However, the most effective way of defending an aggressive Fizz is the presense of your jungler, Please remember this. Also please remember, the price you pay for feeding a Fizz, Katarina or Akali is HUGE!
  
  Here are some things you need to know before rushing this item:
  
  1. It does not provide any mana regen or CDR. So buy Doran's Ring on your way to Abyssal Mask. You can even try triple Doran's Ring to secure early lane dominance over the enemy laner.
  
  2. Getting tankier against AP burst might not be a comfortable thing to deal with as first, as you may have got used to panic spell popping. Don't waste your summoner spells and your stun. You can lead the enemy to turret range and cc them when they fall back.(just stun Katarina when she is ulting)
  
  3. Always get some HP pots in hand, since no item in sight would provide you any HP sustain.
  
  4. Always buy wards when you have space for it. Nothing can save you when you are auto-attacking turret and the enemy jungler and mid laner jump on you together.
  
  5. Buy vision wards when you have space. FOR Akali.She can jump on you, but she cannot escape if you have vision ward. It is only way that you counter any stealth champion.
  
  6. The aura also works on minions and wraiths, therefore it helps you so much when you are doing cs and wraith. Take that into account.
  
  7. The effect of this aura is even bigger when it comes to late game, as your damage and your flat penetration get higher. With Haunting Guise, Sorcerer's Shoes and Void Staff, your flat penetration is huge, and this additional aura can destroy any bruiser (like Riven, Talon and Zed) who only stack physical damage. Your whole set of penetration can turn their magic resistance to negative and insta-kill them. But you are safe, since you have Zhonya's Hourglass to save your life and Exhaust to disable the enemy.
  
  8. You still need mana sustain and you cannot take triple Doran's Ring for the whole game, right? Definitely get Morellonomicon after Abyssal Mask. Ask for blue buff whenever you can take it. Blue buff is the best mana sustain tool, EVER.
  
  9. I personally prefer buying Negatron Cloak first over Blasting Wand due to the following logic: your goal is not to poke hard, but get enough cs in lane. If your enemy laner is weak and you beat him like 4/0 early, why bother buying Abyssal Mask? Just rush Morellonomicon, Deathcap, even Mejai's Soulstealer! If you really need this defensive item, make it defensive first. I would buy Negatron Cloak and Doran's Ring together after first back to make sure I have enough mana sustain. I'm not an aggressive mid laner and I know every mid assassin is more aggressive than I am, so I would just play defensively and do some farming. In early and mid game, he is more scary, but in late game, you are the god. In case you face a mid AP assassin, calm down and do some nice and safe farming. You out-scale everyone later.
  
• 
  Yes, I LOVE THIS ITEM, period.
  
  When I struggled in silver ranked games where I carried lots of games but cannot win because of my "huge but not decisive power" in late game, I got lots of defeats with my own KDA like 20/3/12. I counted this kind of games to 3 and decide that I can get a stealer whenever I find my enemy mid laner is weaker than me and I can get some early kills to carry the game. You can also do this when you find yourself scales well and leads pretty hard in cs. Since Xerath is the safest champion in League who never risk himself in the front line, your stack is free stack. If you think Mejai's Soulstealer is a risky item, then picking it on Xerath lower the risk of it pretty hard.
  
  Once you pick this item and get some stack successfully, you force your enemy to focus you, which is even worse for them because they cannot really touch you if you position and ward well. As time goes by, your AP becomes so scary that even full tanks cannot take your combo and still stay. When you hit 20 stacks, CONGRATULATIONS, YOU HAVE RECOVERED THE TRUE Xerath, THE OMNIPOTENT MAGUS.
  
• 
  I rush this item whenever I face an AD bruiser like Zed, Yasuo and Talon.
  Seeker's Armguard gives you 30 armor, 20 AP and it charges up to 45 armor and 35 AP after farming five waves of minions. Similar to magic resistance, armor uses the same formula. Let's say you buy Seeker's Armguard at lv6, and your armor becomes 16+3.5*6+30=67, and it goes to 16+3.5*8+45=89 whey you are around lv8 to lv9.
  
  At lv6:
  With Seeker's Armguard: 100/167=0.5988
  without Seeker's Armguard: 100/137=0.7288.
  It reduces your physical damage take by 13 percent instantly, together with 20 AP.
  
  At lv9:
  With Seeker's Armguard: 100/189=0.5291
  without Seeker's Armguard: 100/144=0.6944
  It reduces your physical damage take by 16 percent, together with 35 AP.
  
  I don't know what you think about it, but I find it to be a pretty nice deal, especially when you have NO OTHER CHOICE! Your enemy mid laner stacks attack damage, and you only stacks AP in order to be useful. As your enemy laner gets more and more cs, his attack damage will become more and more scary, which makes it more and more risky staying in lane without and protection. I have seen another Xerath laning against Talon without Seeker's Armguard, instead he bought Fiendish Codex+ Doran's Ring and came back to lane.(This set costs 60 more which might worth 2 hp pots) What he got is this: he got insta-killed twice by Talon and Kha'Zix comboing him together.( Kha'Zix just ulted and Talon just jump in and combo) What do you think? I do not like it at all, so I would just pick Seeker's Armguard all the time as first item, then go to regular items like Morellonomicon. Again, blue buff is crucial to you at this point because you have no additional mana sustain. Buy a Doran's Ring together with Seeker's Armguard might be even better but you can rarely have the chance to sit on so much gold then make recalls against any AD mid bruiser/assassin. Also, Exhaust is nice when you are playing against Talon and Zed who can burst you in one combo, also almost secures a kill when your jungler comes to get Yasuo as he has no escape but only Flash.
  
  
• +
  First of all, these two items can come in pairs because Liandry's Torment's passive is amplified with Rylai's Crystal Scepter's passive slow. If your enemy team is building HP, this pair of items is very effective, especially when your team is sieging and you are poking. This pair of items also provide 800 hp, 150 AP and 15 magic penetration, which are lots of useful late game stats. However, a good team will not give Xerath the time to poke enough and just start a teamfight as soon as possible.
  So where are we standing now? you will have at least one open space for either of these items. What should we get? I recently had a second thought about Liandry's Torment and I think it does not fit on Xerath since it provides too little AP, and it costs too much. The problem is that Xerath cannot maximize its passive, and I personally think this passive is not that strong against tanks anyway. If I am not facing any ap laner early, I will have four items: Sorcerer's Shoes, Athene's Unholy Grail, Rabadon's Deathcap, Zhonya's Hourglass. I definitely recommand Void Staff as your fifth item because it provides you at least 10 magic penetration if your enemy has only 30 magic resist. It also provides 70 ap, and only costs 2295!!! My mastries also give more 6 percent of magic resist ignorance, which yields 41% together with Void Staff. Then you can go Rylai's Crystal Scepter as your last item since it gives you large amount of health, 100 AP which is very high, and a decent slow. Every AP laner has the experience of forgetting to use Zhonya's or your "1" button just does not respond in time. Therefore that 500 health may even save your life and win the game. Also, buy blue and red pots when you are on the way to your last item. Guess you have seen froggen's Xerath glowing all the time after mid game.
  
  In a word, I do not really recommend Liandry's Torment on Xerath and my preference is Void Staff>> Rylai's Crystal Scepter> Liandry's Torment.
  (to be continued)
• (Please let me know if you think there are other potential item paths out there)
  

• During early laning phase, your primary goal is to get as much farm as you can, and punish your enemy laner whenever you see the chance. If you have enough mana to spend and the enemy laner does not zone you hard out of lane you can spam a little bit more skillshots to keep your enemy dodging. Be really careful with lane pushing as your mana would run out pretty fast if you have to farm with skillshots and it's so easy to miss your e when enemy jungler jumps on you from bush. Ask your jungler for gank if the enemy is zoning you out. It's actually pretty easy to zone an oom Xerath out of lane in early game but it might be also dangerous, as he would have Mana Surge in hand when he starts chasing enemy with the jungler. One auto-attack would give back the mana for a full combo and your lv2 Eye of Destruction which hits in the center has a pretty significant slow effect. You can then land a long-range Shocking Orb to root the enemy for 1.5-2 second. This costs at least a Flash.
  
  Here is my experience:
  
  1. look at the minions--find the minion your enemy laner is going to farm--predict the place it is going to stand when it makes the attack or skillshot--Poke
  
  2. Start charging your Q--your enemy laner begins to dodge in the direction parallel to the minion line--you lead the enemy a little bit to land--learn his dodging pattern, next time fire according to his pattern.
  
  3. You charge your Q--your enemy laner begins to fall back to turret--wait for your Q to go off or just fire to take farm--Land W on the enemy when it is trying to come back.
  
  4. Predict enemy's next farming move--land W and throw out E at the same time--auto-attack the enemy to surge mana--go back and fire your Q. (If your enemy is in low HP at this point, keep chasing as your Q has pretty low cooldown and can fire again shortly. If you can land this second Q, you can probably ult it down)
  
  5. Stand at the back of river and snipe them outside your enemy's vision.(If you don't know where I'm talking about, think about where you can stay safe and unseen at the same time)If they put a ward on one side of your river's highland, snipe from the other side. Also buy a pink at your blue or red buff side bush to clear any ward that they may put down. Pink ward is always your friend.
  
  6. Usually people start with Doran's Ring, and this give you around 40-50 AP depending on your runes. This gives you an unique advantage as Xerath since you can Q-W one combo down range minions, which is extremely effective at pushing your lane. Comparing to [[syndra], she has to reach lv7 to have her q at rank 4 so that she can Q+W one combo down ranged minions.
  As you can see, Xerath has many ways to land skillshots, and this is why he is good in laning phase as long as you can land some skillshots and surge enough mana. However, since you have no escape and your stun is not every effective compared to other mages' cc like Lissandra, Syndra, Lux, etc., you need to keep the distance and abuse your range advantage. Use your skillshots to force the enemy dodging then you can go back to minions to do farming and surge mana. Always try to surge mana, as it is free.
  
• Another thing I want to talk about is warding. This is so critical because Xerath only has a stun which may or may not land(compare to Syndra), and he can only use summoner spells to escape. Here are the tips:
  1. Try to ward Wraith in enemy jungle to maximize your vision and bait the enemy jungler for an anti-gank. As long as you play safe and stay on the warded side, you will not die out of ganks. Just keep up the farm and poke the enemy down.
  
  2. After your first recall from lane, consider buying additional Stealth Ward to alert your team if your enemy laner is roaming. Always be aware of anything happening in the jungle, as your Rite of the Arcane may save your jungler and bot lane in one second.
  
  3. When laning against Talon, Akali or the enemy jungler is Kha'Zix or rengar, consider buying a [[vision ward] and put it on the edge of your turret range.
  
  4. After your second or third back, consider selling all hp pots and save space for wards. I would feel extremely uncomfortable if I leave base without any wards.
  
• Roaming is an important part of laning, and it is a little bit different for Xerath from other laners because he has no escape. Do not roam if you have no vision around dragon, since anyone except the enemy support can kill you in 3 sec, and no one is going to help you out.(from my experience, never trust your teammate saving your life. As a Xerath, you save yourself) Also since your Shocking Orb travels slow and easy to dodge, any close encounter will cost you at least one summoner spell. If your duo bot run out of wards, ward the small bush near dragon.
  After some nice warding, you can roam after you reach lv6. Simply roam when you see a chance in bot lane and fire your barrages to any low hp enemy. Do not spend too much time sniping as the enemy laner and jungler will react and catch you ASAP.
  
• Backing is simple for Xerath: try not to back as long as you have enough mana sustain and full hp, since pushing hard helps your team secure dragon and buffs. Throw all your skillshots at the minion line and make recalls. Buy AP before magic penetration, and get enough AP before you fight near dragon. Never forget wards.

In general, Xerath is very strong at long-ranged poking and mana sustain, therefore whoever has hp sustain and effective gap-closing abilities is a threat to Xerath. However, since you have mana sustain and long range, you can actually play against any champion in the lane and farm evenly with your skillshots. This is actually more about the experience of staying safe yet harassing effectively, and communicating with your team in time. I would briefly talk about each possible champion you would face and the things you should take advantage or be aware of.
One thing I need to mention is how far you should stay away from your enemy. When I talk about stay away I usually mean 2/3 of your screen since most gap-closing abilities can go through distance of 1/3 screen.
Here is the strategy(which is also the major strategy you should take when you are playing against any champion): when your enemy is standing behind minions, go to the minion line and surge mana as much as you can. This is most likely to happen when you have won trades early on and your enemy is playing safe. Just still keep far away from your enemy and push the lane into turret and ward on side of the jungle. If your enemy ever comes close to you, 99 percent likely the enemy jungler is near, so fall back ASAP. Just escape to the other side or back to turret. Never be afraid to pop-up your summoner spells since it would be too late if you got caught. Buy boots early, sometimes it helps A LOT! Ahri is a threat to you because she can heal herself, also has VERY effective gap-closing ability Spirit Rush. Most Ahri players build burst and do not buy mana sustain, which is the thing you should abuse: just poke her as much as you can from afar after lv6 and keep very long distance from her. The real threat to you is her Charm since it is like the active of DFG, and disables you for pretty long period. However since her Charm cannot go through minions, you are safe as long as you are standing behind minions and the only thing that can hurt you is her Q. Ask your jungler to gank mid pre-6 since she is kind of scary after lv6 if you wanna fight on on her face. Again she is burst champion and you are not a burst champion at all before late game but a good harasser, so take your advantage. Also learn her Q range and dodge it as much as you can. An OOM Ahri is the best thing you can ever have as Xerath, so force her to farm with her spells rather than auto-attacks.

There is a general principle when Xerath comes into teamfight: stay back and spam your Arcanopulse. Here are the tips:

You are the most effective late game harasser in the league and you have your passive to sustain that constant harassment.

When the fight begins, make sure you do as much damage as you can rather than chasing one isolated target, also ult down the squishy carries when you are safe.

Focus any enemy AD bruiser who's trying to catch you and your adc. Do whatever you can do to juke and kite the enemy.

Make sure that you get around 40 CDR when the game lasts for 25-30 minutes. The rate that you fire your skills decides how useful you are.

Watch your adc if anyone is trying to take him down. You stun and slow can disable that bruiser and you guys together can nuke him to dust in one second. I'm repeating this because you do much better job in kiting when it comes to late game as your adc's attack speed gets super high, and he has to stay still to do damage. Save your adc if you still have some space to kite.

Put a pink ward or activate your Oracle's Lens when the fight begins. This weakens those stealth bruiser badly. Trust me, you will be the only one doing this 99 percent of the time since low elo players have no clue how to deal with stealth.

Your ult is not a single target spell and it does crazy damage in very short time. If your team have some nice crowd controll chains that can lock people down, your ultimate can do the maximum damage to their whole team and this helps so much in the team fight. No matter who that target is, fire it as fast as you can because you still have your regular combo available and you need to throw them out too. Do not fire them on the enemy adc if you team is not focusing him since you cannot take him down with your ultimate anyway, and he has crazy lifesteal which will heal off your damage.

One thing unique about Xerath is that he need to adjust his position frequently during the teamfight, so he needs some space for that. This makes him a nice siege champion, but not a good defensive champion.(for Baron and Dragon, not turret though) Stay away and safe from your team when you guys are taking down baron or dragon, and this makes you survive longer. The crowd controll will be all on your team but you, and you have enough space to adjust your position. Take baron for example, when you guys are sieging baron, stay to the left of baron rather near it. Just make sure you can land all your skillshots on baron and that's enough. This also give you enough distance to maximize the length of your stun if the enemies are coming to fight you. One final thing, when you guys are fighting under dragon or baron, nuke the enemy jungler.

http://na.lolesports.com/eu-lcs/2014/split2/matches/week-9/gambit-gaming-vs-alliance-0

This game is the first time you can possibly see a Xerath in LCS. They banned Fizz, Twisted Fate and Kassadin, together with some junglers who have good early ganks. Then Alliance locks in Gragas and Xerath without any knowledge about which mid Gambit Gaming is going to pick. Again Xerath is a strong mid pick if Fizz and Kassadin are banned away.

The way Froggen plays Xerath is so clear and simple: picks up as much farm in lane as he can, and focus on teamfight positioning.

At around 11 min in game, you can see why people say Xerath has very effective Dragon and Baron control: he just snipes Rengar out so that they cannot get the dragon and later secure it for himself.

At around 15:30 in game, Xerath combos Syndra from very far range when they both have almost the same AP. As I have said before, no one can lane against Xerath after early game because no mistake is tolerated.

At the teamfight around 18:40, Xerath roams to bot lane first, with the river all warded. The warding is very important because this secure the path for Xerath. He knows where Syndra is so that he can decide when to go back to lane and poke Syndra to keep hinmself safe. This is why I put wards into core items: warding is life to Xerath. Of course you should have seen that those wards are actually team efforts. (at around 18:20 Braum and Corki when to backside bush of south red buff to secure vision)

As you can see, the area of presence of Xerath is pretty small. He does not really roam. He does not have to , and it is actually very dangerous if he goes down to bot lane too much.

Finally, look at the team formation of alliance: Xerath is at the very far back line, behind anyone else.

Thanks for reading, hope to see you mastering Xerath soon!