As Scion woke up, he put a curse under Leo, which made him transform into a lion, and not even the three wise men could help him.
Many of Leo's soldiers had been taken by mentioned wizard and also, Hauzer was awiting him outside, and thus, Leo's journey begins, in search of his soldiers, to defeat Scion, and specially, to pull off his curse.
When he was in his journey, his first obstacle was hauzer, a giant fossil that resembles a T. Rex(though, confused oftenly with one) which was revived by Scion, Cue fight starts.
After He defeated hauzer, he encountered the three wise men, as they were telling how Leo did a good job killing Hauzer, but it was too late, because Scion scaped and grabbed a soldier(Blade(not mentioned)), and that he might even have a "twisted scheme" behind him. Because Leo is a man of word, he promised the three wise men not to fail them.
See also: Blade(Villains wiki)
Leo when completes his journey through land, he finally goes to darminor to confront the one wo put the curse under him.
As Blade was greeting Leo, Leo had an horrible reveal, that Blade was Leo's kidnapped bodyguard after all, since he recogniced his voice, but (brainwashed) Blade didn't care, as he was saying he's no longer in "mortal's world", Leo promised him an honorific death. Then the battle starts.
After Blade was defeated, he went concious again, and decided to take remorse on the evil actions he did, after revealing the location of his brainwasher, Blade dissapeared, Leo, as he was mourning over Blade's death, he went to avenge his friend, by killing Scion.
As Scion appeared in the scene, Leo was telling him the wrong actions he did, but Scion considers him a messiah, who thinks he's doing right,and that every human should call him "God". The battle begins.
When Leo finally defeats Scion, the three wise men appeared, as they were admiring Leo, but also telling him there's a thing that he's lefting, you can decide his fate depending how you play.
Bad Ending(Dismember blade): If you finish blade by dismembering him, after Leo defeats scion, he ignored the wise men advice and decided to continue, this didn't help his curse, it got worse, untill he was transformed into a full lion, the citizens of Greedia wondered where's Leo, they find nothing but a lonely lion.
Good Ending(Don't dismember Blade): Only if you finish Blade by contundent hits(Kicks), Leo does follow the advise of the wise men, and he reconstructs his kingdom, he wasn't totally free of his curse, but at least, it stopped.
Best Ending(Not continues): If you dont use ANY(read, any) continues, you will get a scene little different from the good ending, Leo's curse finally vanished, he was no more lion, and he recovered his human form.
He's the biggest protagonist of the game, with an height of 2,18 M (7Ft, 2In).
He acted as an special guest in Capcom Fighting Evolution, and also, as a cameo in Puzzle fighter in Akuma's stage and also in UMVC3 during Hawkeye's ending
He's the only protagonist who didn't change name in the western localization.