If a player dares to enter the Dungeon in a world where Skeletron has not been defeated, they're in for a nasty surprise! Dungeon Guardians, the formidable guardians of Terraria, will spawn and attack the player. These dungeon guards are practically invincible and can generally kill most players with a single hit. So, it's best to hit da bricks, skeleton, and defeat Skeletron before venturing into the Dungeon!