The Eris Coin is located at co-ordinates B-2 in the Cavern of the Gods, in the secret passage underneath the Pillars of Shadow, between the Altars of Isis and Horus. The coin only appears after re-opening the temple. The "blip", located in the southern section of the co-ordinate, also has 2-3 Cinderella Sea Slugs inhabiting it.
- The celestial body engraved upon this coin is the dwarf planet Eris, which was originally classified as the solar system's tenth planet. However, it has a slightly smaller diameter than Pluto, which is classified as a dwarf planet, and thus Eris is a dwarf as well.