Veigar

Strengths

Use Event Horizon to increase your chances of landing Dark Matter.
Veigar is extremely Mana and Cooldown Reduction dependent. Try buying items with these stats in order to increase the effectiveness of your passive and Baleful Strike.
Veigar is very fragile. It is valuable to select at least one summoner spell that can be used defensively.

Passive · Phenomenal Evil Power — Veigar is the greatest Evil to ever strike at the hearts of Runeterra - and he's only getting bigger! Striking an enemy Champion with a spell or scoring a takedown grants Veigar permanently increased Ability Power.
Q · Baleful Strike — Veigar unleashes a bolt of dark energy that deals magic damage to the first two enemies hit. Units killed by this bolt grant Veigar some ability power permanently.
W · Dark Matter — Veigar calls a great mass of dark matter to fall from the sky to the target location, dealing magic damage when it lands. Stacks of Phenomenal Evil reduce Dark Matter's cooldown.
E · Event Horizon — Veigar twists the edges of space, creating a cage that Stuns enemies that pass through.
Ultimate · Primordial Burst — Blasts target enemy champion, dealing a large amount of magic damage, increasing based on the target's missing health.

A suggested 5-lane lineup built around Veigar, based on hero partnerships and role synergy — not win rate.