Who they are
Most people in Runeterra don't fear yordles. Yordles who live among mortals usually return to Bandle City with new stories, but some lose their way, and the sorcerer Veigar is one of them. After the Great Darkin War ravaged the world, the survivors in Valoran looked to the stars and revived an ancient celestial magic. Veigar was fascinated by it and believed he'd mastered it. He joined an order of mages in the lands of the Noxii and taught them to find hope in the movement of the stars.
While others rebuilt the world, Mordekaiser and his armies conquered and enslaved those lands. The order's mages were useless in war, but Mordekaiser noticed Veigar and understood what he really was. He seized him and carried him off, and the other mages were slaughtered. In his vast fortress he forced Veigar to serve the darkness with his magic and bound him to the material world, so he couldn't escape to Bandle City. For a yordle there's no crueler torment. Mordekaiser's empire ran on fear, and Veigar watched his captor come close to immortality. He lost track of time. His magic and his appearance twisted, and his memories faded, until he no longer remembered why he'd come to Valoran, where he was from, or whether he'd ever had another life.
When Mordekaiser's own followers brought him down, Veigar was barely recognizable, with burning eyes and a spiteful voice. He escaped his enchanted cage, but instead of turning his back on evil he embraced it: he put on sinister sorcerer's armor and set out to earn respect through ruthless villainy. The people of Valoran did learn to fear him, a little, because he burned pastures and wrecked a baron's manor. Some of his deeds are strange and maybe even helpful: he drives off bandits, and the remains of wild wolves turn up in a town square. He always falls a bit short, but his goal hasn't changed: to become the most evil villain in the world.
