The surface of Remora.
Remora was a planet in the same solar system as Rock, Fire, Bone and Ice planets. Unlike the other planets, it did not support life. The Beast's advance forces conquered it and turned it into a giant battle station in preparation for the Beast Planet's arrival.
When Pyrus and Zera crash-landed on the dead world, they discovered the massive Beast battle station inside of it, and convinced the Alliance to launch a full-scale assault against Remora. The Alliance fleet was nearly wiped out by Remora, but the planet was destroyed when Jade convinced Lord Mantel to lend his Battle Moons to the assault.