|List of all locations|
Grune's Tomb is a large underground vault that serves as a prison for Grune the Destroyer. It is located under a giant tree in a grassy plain on Third Earth. The entrance to the tomb is hidden under the tree. The door to the tomb has a magic seal on it that prevents Grune's spirit from escaping.
Once, while trying to seek shelter from a raging thunderstorm, the Bolkins Bundun and Hurrick accidentally stumble upon Grune's Tomb. While trying to force their way into the tomb, they inadvertently end up destroying the magic seal, thus freeing Grune. It was eventually Jaga and the Eye of Thundera that banished Grune.
Later on, Mumm-Ra summons Grune to New Thundera from his tomb. Grune then proceeds to attack the ThunderCats and even succeeds in breaking the Sword of Omens' blade. But Lion-O eventually sends Grune back to his tomb and seals him inside it.