Trinexx

Trinexx is the boss of Turtle Rock in A Link to the Past and the last dungeon in Ancient Stone Tablets. He is like a turtle with three heads: one in a normal position and two others protruding from it's shell on stalks (red and blue). In order to defeat Trinexx you must use your Fire Rod on the blue head to stun it and hack away with your sword. Repeat that with the Ice Rod on the red head until it's destroyed. It helps to destroy the blue head first, since it will create a permanent streak of ice on the floor if you let it, which can impede your motion. Also, on the second head, it lashes at you with the stone head. During all of this, you must avoid Trinexx's elemental attacks (red shoots fire and blue shoots ice). After killing the colored heads, Trinexx becomes a giant snake with a strange glowing orb in the center of his body. Hit the orb three times to defeat the boss and win the dungeon's Crystal and Heart Container.