Leo is the first Lord of the Thundercats and founder of the city-state of Thundera. He was the commander of Mumm-Ra’s forces during the evil Mummy’s reign and is Lion-O’s ancestor. Panthera and Leo planned the overthrow of Mumm-Ra and in a stunning turn of events Leo secures all four Powerstones and activates the Armour of Omens, which powers him up enough to defeat Mumm-Ra. Leo then divides the powerstones between the races and establishes the ThunderCats dynasty.
Leo and Lion-O shared many qualities. They both were naturally skilled in battle and cared for the animals being subjugated by those in charge. They both had soft spots for strong female Cats (although Leo had more success in this department). In many ways Lion-O takes after Leo more than he did his own father Claudus.
21. Birth of the Blades
25. What Lies Above, Part 1