|List of all weapons & other items|
The Keystone is an ancient powerful crystal. This emerald colored crystal has ancient writings and symbols carved onto it. The Keystone is a source of pure and unlimited energy. Such is its power that it is able to revitalize not only living beings, but also mechanical objects like engines. However, it is also incredibly addictive and anyone one who uses it becomes a slave to it, eventually being destroyed by the Keystone.
The Lunataks Alluro and Chilla once set a trap for the ThunderCats by sending a false transmission in which they claimed that the Keystone was a piece of the Treasure of Thundera. They did this to lure the ThunderCats to the dangerous Crystal Canyon of Third Earth where they were waiting to ambush them.
The Lunataks' attack severely injured Lion-O as well as injuring Lynx-O and Tygra and damaging the ThunderStrike. Tygra then retrieved the Keystone from a nearby cave and used it to heal all of their injuries and repair the ThunderStrike as well. Unfortunately, Tygra became addicted to the Keystone and would have been consumed by it but Lion-O eventually used the Sword of Omens to break his addiction. In a battle between Tygra and Alluro, the Keystone was destroyed.