The Altar of Osiris is a room located at coordinates C-2, the Northeastern corner, in the Cavern of the Gods in Endless Ocean 2. This room represents Osiris, the god of underworld.

This is first seen at the end of the main plot in Endless Ocean 2. After losing GG for soome then unexplained reason, the diver swims into this room and plays The Song of Dragons on the dragon flute and it responds back.

The currents outside then pick up and sweep Oceane away and the player swims after her.