The Moon Lord is the final boss of Terraria as of version 1.3.5.3, and drops a majority of the endgame items, such as the Meowmere. It also drops the end-game ore, Luminite, used to craft many endgame armor sets and tools. He is summoned by defeating all four of the Celestial Towers from the Lunar Events, or by using a Celestial Sigil.