Leo, was the commander of the Black Lions. He was the second prince of Grimwar and was greatly known and respected for his brains and brawn. He was considered more beautiful than his older brother, the future king of Grimwar. 

The people of Grimwar had the ability to turn into any animal if they were descendants of the gods. Last names typically indicated what family had the most power and influence over the kingdom. The royals were known to have the ability to turn into a lion of any kind. Royals had the ability to bestow their great power to an entire army if they chose and Leo's father did exactly that.

The Black Lions were also the name of the Grimwar army and were based off of the royals ability to shift into their lion form.

Leo was known to be the largest lion in history and had the blackest, darkest fur of any. The ability to shift into his animal made his body sick at times and it took him a while to recover fully.