Tirek is a villainous centaur who made his debut in the TV special My Little Pony: Rescue at Midnight Castle. In the special, Tirek is the ruler of Midnight Castle, which he took over from the previous ruler, a prince whom Tirek subsequently turned into his minion Scorpan. Tirek aims to capture four ponies to transform into savage dragon-like beasts that would pull his Chariot of Midnight. He is armed with the Rainbow of Darkness, an energy that is capable of corrupting any living thing it envelops and has the potential to bring about eternal night.
In the My Little Pony: Friendship is Magic fourth season finale "Twilight's Kingdom", Tirek is an escaped prisoner of Tartarus who seeks to steal all the magic of Equestria. He originally attempted to do so long ago, but was betrayed by his brother Scorpan and banished to the pits of Tartarus. This incarnation of Tirek has the ability to orally siphon a pony's magic and add it to his own, allowing him to become larger and stronger with every pony he leeches off of.