This is my seconds guide, this time for Xerath. I like using him a lot and probably one of the most fun champions I have played because you have to predict where the enemy will run to and other stuff like that when you try and zap'em with Arcanopulse. Also if you have questions, leave them in the comments and I will possibly put them in the guide.

Also, notice how there is 2 Xeraths, one is for dominion, one is for Summoners Rift. How can you tell them apart? One of them has the spells Promote. Also for each section I will include a dominion part, and a Summoners Rift part.

Summoners Rift
Pros:
-Most range of all the AP champions in the game when he is in Locus of Power
-Can farm and harass at the same time with Arcanopulse
-Can even kill tanks due to MP from Locus of Power
-He had a blend of Chemical X in his skins. :)
Cons:
-His passive doesn't help much.....
-Very vulnerable to cc
-Hard to place in a good place
-Easily countered by charging champions
-Needs a tank on his team to do well

Dominion
Pros
-Still has the longest range of all the characters
-Makes a great interrupter when enemies try and capture a point
- Crystal Scar Aura allows him to actually kill someone in one go
-Guaranteed to have enough money to dominate
-Can be attacker or defender.
Cons
- Asceneded Form is more useless due to Crystal Scar Aura Armor Penetration
-Still squishy
-Can't take on melee like he can on Summoners Rift.

RUNES
Pretty basic rune setup.... CD for more Arcanopulse fun, mana for early game, after you get Tear of the Goddess no more need for more mp5. If you wondering why not grab health quintessences, your range from Arcanopulse and Locus of Power should keep you away from harass. If you put AP quintessences instead it make stronger harass too so even better!
MASTERIES
..... Comment if i need to add this
SUMONER SPELLS
Teleport
Why grab this instead of Flash? Well thing is that if Xerath got into range such as... Kassadin, Xerath would most likely die........ Teleport allows you to kill a champion and get back in a lane, or get in position for a gank on top or bot if they have a ward. Or if you have been ganked and need to back, you may do so.
Ignite
For those times when Kassadin Riftwalk's into your face, after his silence is done he is dead with ignite and your combo (explained later).
Alternative Sumomoner Spells
Flash
Eh well i guess in some cases its useful when you have that Akali on the other team or Xin Zhao. For those champions who have a dash, might want to grab this if you can in ranked matches.
Exhuast
If you know they are melee heavy (3 or more melee) this might save your life.
Cleanse
Not hugely recommended unless you see heavy cc teams.
Ghost
In learning phase.

Dominion
Runes
Pretty basic once again, the only thing i suggest is that you can go either AP or hp quintessences, either works.
SUMMONER SPELLS
Promote
So your point is to push and conquer or defend? Your job is both actually Promote allows you to push faster or win a lane so the minions will take one for the team. Also gives you additional gold and exp for each minion killed. Pretty useful.....
Ignite
Most of the time in dominion, you are going to get charge. need examples? Akali will Shadow Dance towards you, if you are able to tag her with Mage Chains and combo off on her later before her Twilight Shroud apperas, you are golden cause the ignite will most defiantly finish her off if she does go in. Also good for that annoying Kassadin or if Shaco Decives into your face.
Alternative Summoner Spells
Flash
In my opinion, other spells are better than this one for Xerath..... So you just combo'ed off on them, they are not dead yet. What do you do? Flash! Now how far away were you while you nuked them? Pretty dam far away.....
Garrison
In case you are one heck of a defensive Xerath i suppose you could grab this one.... good for tower diving but sometimes it just doesn't matter because his range is so ridiculously long.
Exhaust
In normal draft? See something like a Tryndamere on the other team? Great spell for him, after you combo off on him, he uses Undying Rage, you Exhaust him, he can't catch you, you get a free get out of jail pass.

Spell Sequence Summoners Rift
Max out Arcanopusle first as it will help you farm and poke at the opponet from time to time. Then you can chose to eaither max Locus of Power if you really want to poke at the opponet hard, or you can chose to level up Magc Chains to kill them quick. Depending on who you face might chose which one you go. Lets say.... Vladimir you can't really kill him so if you do face him you want to be farming mainly. so go with sequence 2. If you face somone like Veigar you should probably go route 1 to make sure he doesn't farm too much on creeps.
Dominion
It's just better to go for skill set 2. More nuke in it and you won't need to poke as much so lower cd on Locus of Power won't do much.

Summoners Rift
Early Game
When you first start off in the lane, you start with Sapphire Crystal, Health Potion, and Mana Potion. By the time you are lvl 6 you should have enough for Tear of the Goddess, if you don't you are not harassing/last hitting enough. If you're facing problems like constant ganking, unavoidable dmg, etc. Grab some Health Potion's with that. Afterwards you move on to Sorcerer's Shoes, which is really helpful with Arcanopulse. Now we move onto the mid game phase.
Mid Game
So you probably wonder if you are going to live 1v1'ing someone, depends who you face. Most the time you don't actually want to fight, you want to harass from afar until they are low enough to nuke down. By this time you should be able to take an opponent down from full health to 1/3 health left if you aim all your attacks correctly. You should have your Rabadon's Deathcap by the end of this phase, and maybe a Blasting Wand or Amplifying Tome.
Late Game
You should have a Void Staff and Rabadon's Deathcap, enough to kill a tank, a dps, anything as long as you are not targeted. You should also have a Rylai's Crystal Scepter to slow down opponents to combo off on them. After that Archangel's Staff should help you a lot. Then you get your last item depending on the enemy team.


Q. Why start with a Sapphire Crystal?
It's an easy transition right into Tear of the Goddess. Once you get the tear, you can harass with Arcanopulse with Locus of Power. Afterwards, you have a lot of mana to try and poke at an enemy, if it fails then you still got more mana!

Q. Dorvan's Ring looks pretty good on Xerath.....
A. No not really, the 15 extra ap and 5mp5 looks good, but the 100+ health won't make much of a difference, you are a mage who doesn't blow everything in one go unless you know you can kill them that way. Also it doesn't provide mana in case the enemy tries to 1v1 you and you don't have enough mana to. On top of all that, it will make it take longer to get to core items, so just no overall.

Q. What are your thoughts on Abysall Scepter?
A. Not useful as all, you are either caught or you aren't. Your long range out ranges the mr reduce aura from Abysal Scepter. Better to grab something else.....

Q. What are you thinking going with no suvivability!? You are going to get killed!
A. Mhm.... only if you are in a bad position you will die, he was already squishy enough, he is a glass cannon champion. Nuke'em or die. Lucky tanks like Nasus can't really take him down because of his armor from Ascended Form and his stun combo. On top of that with this much magic penetration with Void Staff, Locus of Power, and Archaic Knowledge , that equals up to.... 40%+30%+15%=..... you just shredded them down to 15% of their MR..... Inconceivable!

Dominion
All packed? Start off with Prospector's Ring and Boots, you may chose to get a Health Potion and a Mana Potion if you like. From here on out you just do your thing and grab the selected items. There is also one slot free of for your last item if needed such as maybe there is an annoying Akali or Twich/ Evelyn. Hextech Sweeper saves the day here, since all your attacks will now give vision of your target, you can continue to chase them as long as you aim all your spells correctly.

One more thing, Since you have the Crystal Scar Aura, combined it with Void Staff, Locus of Power, and Archaic Knowledge , the opponent has 10% magic resist now... Even more Inconceivable!

Early Game:
Gamer: ALRIGHT! Just entered, now to beat the **** out of them! So lvl 1.... I am super weak...
Yea Xerath is not the greatest at lvl 1, you can try to harass with Arcanopulse depending on what champion you are facing. Want an idea how big his range his on Arcanopulse? Take Kassadin's Null Sphere and add a few yards (or w.e. the unit is) surprisingly, it outranges Null Sphere, and here is another thing, Xerath vs. Kassadin lannign phase, Xerath wins! When combined with Locus of Power, it equals Kog'Maw's Living Arillery range at lvl 1. Pretty insane huh? When possible, try to harass with Arcanopulse to hit the champion and as many minions as possible. Also, take note that Locus of Power is free to cast, so its better to combine Arcanopulse with Locus of Power while harassing.
Mid Game
Now you are powerful enough to take down an enemy from afar using your combo, Mage Chains, into either Locus of Power if the enemy is close to you, or Arcanopulse if your target is running away, after wards combo up with 3 Arcane Barrage'es then Arcanopulse them again, if needed or facing a Swain, Ignite after. If possible you can combo all this off while in Locus of Power to deal even more dmg. Also, if possible let's say bot has a ward, you Teleport to that then you go in for the gank. Most of the time this should work if the enemy is pushing the bot turret. If you see no gank possible, continue to farm and try to push down a tower or two.
Late game
Couple of tips.
1.Are you scouting ahead? Don't do it you are going to get jumped.
2.Are you with your tank while fighting? If not, try not to stand in one place until the enemy finds you.
3.Are you facing a feed team? Hide behind your tanks, in a brush anywhere!
4.Are you in a good place to nuke? You better be or else like i said before you are going to get nuked and die. It is preferable you are in range to land Mage Chains though.

Dominion
This part can go either 2 ways.

Offensive
You go top lane with a couple of your partners, if the enemy is faster than you guys, make sure you interrupt them with Locus of Power+ Arcanopulse. When you can, see if you can hit a target with Mage Chains into Arcanopulse, it does a lot of dmg and it stuns the enemy so your team can attack them.

If you win top.
Stay up there and defend it. Or if you really want, leave someone else there and kill others. Your personal choice. I like to defend top usually if this does happen
If you lose top.
You can switch with you defender on bot or continue to try and take over top.

Defending
Like the lanning phase of Summoners rift, if the enemy is in range and you can hit him through the minion waves, do so it really does help in the end.

You end up taking over their bot tower
Best case scenario.... you keep defending bot tower until you die. You can stay there for quite a surprising time, just make sure you are in the fog and wait for the opponent to try to take it over. Locus of Power into Arcanopulse to interrupt them, then hide into the brush. Most of the time you can nuke'em in the brush if you do get to this.

Your turret is taken over.
..... How did that happen? Usually this does not happen unless you are 2v1'ed which is almost never the case because the enemy went top turret. If this ever happens to you, defiantly leave me a comment how they did it.

In my opinion how good Xerath is on the Dominion guide.

Capturer Xerath 1/10 - He just can't.... way to slow with only one way to get out......

Taker Xerath 9/10 - He is unbelievably strong at taking over a tower.... He can kill you on a point from the brush. His range is that ridiculous. The problem most of the time is that the enemy will run away after seeing you... Inconceivable!

Disrupter Xerath 5/10 - Not only can he interrupt casting, at the same time if the enemy tries to find him, they will get quiet a surprise from his combo..... but he has no global so he can only disrupt so much

Defender Xerath 9/10 - He can easily defend a point by luring an enemy into the brush located near it. All you got to do is wait for them to start channeling, then Locus of Power into Arcanopulse then they will do either of 2 things.

1. Try to find you.
If this is the case, just stand by the brush and get ready to combo them down with Locus of Power into Mage Chains into Arcanopulse into Arcane Barrage and finish it up with one last Arcanopulse and if needed Ignite.

2. They run away until 2 of them trying to take it.
If they are apart from each other and you can't get them both with one Arcanopulse, hit one of them with Arcanopulse and nuke the other one down using Arcane Barrage. If you know you cannot handle them though, interrupt them, then run away.

Don't worry yet, this is not the end. I just wanted to put this out before other peole posted builds like this. Just remember that you need to be in a good position and you need to harass to win.