Power Stones, which, if attached to the Sword of Plun-Darr, would give him ultimate power. By managing to take the Warstone (which would later be known as the Eye of Thundera), the ThunderCat known as Leo (with help from the other animals) was able to defeat Mumm-Ra and strip him of the other Power Stones. But when Mumm-Ra's spacecraft was pulled into Third Earth's atmosphere, he entered his tomb to escape the crash and leave everyone else to die. However, the controls were damaged and Mumm-Ra was trapped within his own spacecraft, as the stones and survivors spread across Third Earth. Many centuries later, Mumm-Ra manipulated Grune into releasing him, and was able to orchestrate Thundera's downfall. Now Mumm-Ra not only plans to obtain the Eye of Thundera, but also regain the other three Power Stones and the Sword of Plundarr while gathering some allies to assist him. Grune (voiced by Clancy Brown) - Grune was one of King Claudus' most trusted generals, and best friends with Panthro. Being very ambitious and power-hungry Grune attempted to prove himself to Claudus for a promotion, but instead Claudus chose Lynx-O, and assigned Grune and Panthro to find the Book of Omens. Grune felt betrayed and drove himself mad with his own paranoia. Eventually, his jealousy towards the king was used by Mumm-Ra to convince Grune to become his follower and serve a key role in Thundera's downfall. However, Grune also intended to betray Mumm-Ra in the long run prior to leading the attack on the Elephants' village to obtain the Spirit Stone there, resulting with Grune getting sucked into the Astral Plane. Slithe (voiced by Dee Bradley Baker) - One of Mumm-Ra's generals and the leader of the Lizards. Slithe serves Mumm-Ra in order for his kind to take revenge on the ThunderCats for generations of persecution. Succeeding in ransacking Thundera, Slithe pursues Lion-O's group before overseeing the search for the Book of Omens and later the Powerstones. Addicus (voiced by Robin Atkin Downes) - A bloodthirsty ape-like barbarian who committed crimes against the Bird Nation and was sentenced to a death drop from high up in his captors' domain. However, Addicus is rescued from the fall by Slithe and recruited to be one of Mumm-Ra's new generals. Accepting the proposal, Addicus is allowed to get his revenge on the Bird Nation as Addicus states that they "owe him a last meal".