Trinexx

Trinexx is the boss of Turtle Rock in A Link to the Past. He is like a turtle with three heads: one normal one and two others protruding from it's shell (red and blue). In order to defeat Trinexx you must use your Ice Rod on the red head to stun it and hack away with your sword. Repeat that with the Fire Rod on the blue head until it's destroyed. 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.