Vel'Koz.
Let’s talk about who or what this Champion is. All the information we know comes through various “leaks” from the community, which is likely Riot’s marketing plan for this champion. Vel’Koz follows the same naming scheme as the other void Champions, (Cho’Gath, Kha’Zix, Kog’Maw) so we can safely assume he will be a void creature. He has a very large eye, associating him as one of Lissandra’s watchers, due to her Frostguard clan’s emblem resembling an eye.
It is an extremaly powerful champion that, if played correctly, can turn even the worst teamfight in his teams' favor. Vel'Koz's real strength is his late game - the laser deals tons of damage, even without the Triforce, and this is my Vel'Koz guide :D

t of the items are pretty self-explanatory. Liandry's is a great item for most AP casters since there's always a slight possibility that your skill combo will not kill the oponent. Liandry's DoT should take care of such cases.

You should always rush athenes grail first as it gives you mana regen that Vel"Koz really needs, especially early game.

Deathfire grasp has a great Active, giving you even higher damage burst.

Q - Always try to proc his passive on your lane opponent during the laning phase. The amount of true damage dealt by this skill is quite high therefore it can help you zone your enemy from the much-needed early game experience. :D

W - Great harrasing tool, can be used when your opponent doesn't expect it when casted in a wall's direction

E - Always use it simultaneously with your E - it has no cast time and its second explosion deals quite a high amount of damage but can be easily avoided when the enemy is not stunned/snared/etc. Your E skill can hold the opponent in the explosion radius for long enough.

R - This skill is especially useful when both enemy or your jungler ganks your lane. In the first case, cast it under your champion so when the jungler gets closer to you, he will be knocked back and stunned for enough time to let you get under your turret. In the second case, cast it on the enemy to give your jungler time to get closer to them.

Ignite helps you secure your kills, nothing new here. Keep in mind that you can ignite an enemy while casting your ultimate. Flash is the only escape mechanism for our tentacle friend. Always take Flash.

However!
You can also pick Barrier instead of Ignite, which gives you a baiting potential. However, I'd use this set only against high-burst enemies, like LeBlanc or Akali : )