King of Sparta, despite the gruff and muscular appearance he's a cunning tactician though he doesn't betray his Spartan origin and fights like a brute. In time of great peril, when Greece was threatened by an invasion of the Persian Achaemenid Empire, he and 300 brave Spartan soldiers managed to hold back Xerxes I's 100.000 man army all by themselves in the Battle of Thermopylae. For three days they fought, and while none survived, their sacrifice gave time to the City-States of Sparta and Athens to regroup their armies and repel the invasion In Fate/Grand Order: Absolute Demonic Front Babylonia

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Leonidas is summoned as a Lancer-class Servant and serves as the commander of the forces stationed at the Northern Wall of Uruk, constantly keeping the invading Demonic Beasts at bay. His positive attitude and teachings give faith to the people of Uruk in their survival and serve as example of the undying spirit of mankind. Leonidas dies turning into stone while making a last stand against Avenger with his Noble Phantasm: Thermopylae Enomotia. Before passing away he reveals his opponent's true name, the terror remembered by all Greek people, Gorgon.