Maximum burst and AP late game scaling.
Burst damage and target access
Hitting a champion with 3 separate attacks or abilities in 2s deals bonus adaptive damage.
Deals bonus true damage to enemies with impaired movement or actions.
Entering brush temporarily swaps your trinket for a Ghost Poro, which grants vision until discovered.
While either you or your poro is in enemy territory, gain adaptive stats.
Heal for a percentage of damage dealt with your abilities. Increases with each unique takedown.
+18 Ability Power or +11 Attack Damage, Adaptive
Gain increasing amounts of AD or AP, Adaptive over the course of the game.
Hitting enemy champions with a spell grants maximum mana.
After reaching 250 mana, Manaflow Band restores 1% of your missing mana every 5 seconds.
Veigar can easily proc Electrocute with [E]->[W]->[Q] because abilities do not need to do damage to count toward the separate proc counter.
If you successfully hit your target with [E] the bonus True Damage will help secure the kill before they even come out of the stun.
Keeping wards up on the sides of lane is one of the most important things you can do as a mid-laner. Ghost Poro, while small, provides very reliable vision.
If you'd prefer to go all-out on damage instead of safety, take Eyeball Collection instead.
The Spell vamp from Ravenous Hunter scales incredibly well with Veigar's natural high damage scaling, allowing you to survive tough fights.
Another great option for getting into [E] range is the bonus Movement Speed from Relentless Hunter.
Veigar is the master of AP scaling and Gathering Storm is the ultimate scaling rune.
If you'd prefer to have a stronger early game, take Scorch instead.
Manaflow Band allows you to sustain in the early laning phase so that you're able to build up stacks and scale your AP into the mid game.