Eris

"What's that little planet in the corner?" "That's Eris. The farthest known planet from the Solar System's sun."

- Grievous and Dooku, looking at a map of the solar system.

Eris is the farthest known planet from the Solar System's sun and the largest dwarf planet (the other dwarf is Pluto). It was only accessible through the device created in Project G.A.L.A.X.Y. General Grievous himself took a great interest in this planet.

The Eris Incident
"Help anyone! This is Eris Colo-" "What happened captain?" "We've lost all contact with Eris Colony."

- Grievous and a Nemoidian captain, receiving Eris' final transmission.

About a month after Eris was colonized Grievous received a short distress message from Eris, the only indication that there was any trouble on the planet. Grievous and his elite unit arrived on the planet to discover sickly Yuuzhan Vong-like creatures (suggesting that the Yuuzhan Vong may have come from the Solar System). The creatures had rampaged through the base killing almost all personnel. Grievous and his troops tried to contain the situation but were overwhelmed and forced to retreat. They made it back to their transport and made an emergency take-off from the planet. The base was abandoned and forgotten.