Lion-O

Overview

Lion-O is the primary protagonist of the series and leader of the ThunderCats, where as he also holds the title of "Lord of the ThunderCats" which is passed down from his father, Claudis. Lion-O appears in every episode of ThunderCats. He wields the Sword of Omens and the Claw Shield. The Sword of Omen serves as his primary offensive weapon, it initially appears as big as a dirk but when he calls out "Thunder, Thunder, ThunderCats! HO!" it increases in length to that of a Borad Sword, it  can shoot fire bolts and can grant him enhanced vision by activating the eye on the hilt using the call "Sight Beyond Sight", the claw serves as a grappling tool. 

Lion-O is from the planet Thundera and is chosen as one of the noble Thunderian to travel to Third Earth in the wake of Thundera's destruction.  On the way to Third Earth a malfunction in his suspension capsule causes his body to age more than it normally should putting his body around the age of 24 where as his mind is still that of a twelve year old, note that he is about the same age as WilyKat and WilyKit despite his overbearing size change and comparison.