The leader of the Thundercats
, a race of cat-people who escaped the destruction of their home-planet, Thundera
, to land on Third Earth
, where they fight a constant battle with S-s-slithe
and his Mutants, and the evil undead sorcerer, Mumm-Ra
Lion-O is the son of Claudis, the blind, yet strong-willed leader of the Thunderians on Thundera prior to the cataclysm. When the Thundercat Nobles were forced to flee, Claudis stayed behind to assure that they made their escape safely. Lion-O was placed aboard to assure that the ruling line of Thundera survived. His nursemaid, Snarf went along to care for the young child.
In order to make the trip safely, the Thundercats all went to sleep in Time Capsules - all except for Jaga, the oldest, who died trying to get the Thundercats to safety. The trip was so long that the Thundercats aged despite the Time Capsules. This had little effect on anyone except for Lion-O, who went from a skinny little child to a powerful man. As the son of Claudis, this man-boy was now entitled to wield the Sword of Omens, left behind by Jaga - who now guides Lion-O like Obiwan guided Luke. The Sword, combined with the amazing Claw Shield, gives Lion-O amazing power, and helps him save the Thundercats time and time again. To summon its powers, Lion-O shouts, "Thunder, Thunder, Thunder, Thundercats... HOOOOOOO!!!"