Veigar

the Tiny Master of Evil

Mage

You deny the darkness in your soul...

The build that broke the game

Sorcerer's Shoes

Rabadon's Deathcap

Deathfire Grasp

Zhonya's Hourglass

Rylai's Crystal Scepter

Void Staff

Why it worked

Baleful Strike paid permanent ability power per kill with no cap, so a Veigar nobody bothered turned into a number rather than a champion. Primordial Burst scaled off the target's own ability power, which one-shot every other mage in the game. Event Horizon stunned whoever tried to leave the cage.