Pros:
*BEST POKE IN GAME
*Two second stun at max range
*When ahead, Can one shot any squishy.
*Super long range ultimate, great in low elo

Cons:
-Super Squishy, no escapes and when jumped on you only have a .5 second stun
-No gapcloser
-Ultimate can be super hard to land

Good options -
Flash - Always take it
Barrier - good against high burst targets, great for baiting
Ghost - can help secure kills and run
heal - I personally never take this but it can work
exhaust - great against assassins like zed
Bad options - Ignite you should never be in range to cast ignite.
Teleport - Xerath needs a summoner to help him survive the laning phase

Xerath is a champion that is very good in teamfights. If possible, try to line his Q up with more than one champion. Stay behind your frontline and poke from afar. A long stun is a great way to kill a high priority target. It is much easier to land one in a teamfight because there are many more things to pay attention to. If you ultimate in a teamfight, it is likely the enemy team will forget to dodge it too.

During the laning phase you should always have wards around. Be perceptive. If the bot lane takes a while to show up to lane, they leashed so you should play towards the bottom side of the lane. Vice versa for top. This is because the enemy jungler usually does their full clear before ganking. They will end up on the opposite side of your lane. Poke Poke Poke. Thats your strength. Learn how the enemy dodges. If they have a tendency to lead you one way and then go the other, use that knowledge to aim in the direction they were running from. Don't use your w unless you know it will hit when someone stops to farm, or they are locked down. You always want to get the most out of this ability by hitting the center. Once you get a few items you can one shot a wave. Just walk up, charge your q and release it in a line and you have yourself some easy farm. If your junglers are fighting, go in to help because you can easily do damage from over walls thanks to your great range. In low elo, people won't know how to dodge your ultimate very well. Aim where they are walking. In higher elo, people know how to dodge Xerath ultimate. Some will walk back and forth very fast. Aim on top of them. Some walk where they came from. Aim on top of them too. The zig zaggers are the worst though. They walk calmly away from you and side to side. This is very annoying. Just do your best

Thunderlords Decree is much better in the laning phase. It will give your e>w>q combo a bunch of extra damage. Sadly, it is essentially useless in teamfights. Deathfire will always let you have an impact due to its burn damage on everyone you hit.

+If the enemy is running but is just out of your Q distance, You can flash while charging to land your Q with ease.
+ If you know the enemy has a dash, use your ult where you think they will dash for style points.
+If you are too close to a melee champion, you can flash away and E them to stun them for longer than you would have if you didn't flash. Then hit them with the center of your w for the 80% slow and you should be safe enough.

Thank you so much for reading! I really appreciate it and I hope you learned something from this guide. I will continue to update it in the future! If you have any questions or comments just comment on the guide, as I check the website on a daily basis.