leonides is your partner that you get at the start of the game

Leonidas come from doom dimension and be your partner he eveloved into omega Leonidas

leonidas was born in the doom dimension and is your partner.when
vladitor evolves into battle axe vladitor drago,skyress,tigeress,gorem,and preyas give him
there power and he evolves into omega leonidas.

Leonidas is this dragon like bakugan that was born in the Doom Dimension he came to
earth.He becomes your partner when you meet him.In the Doom Dimension when you face marduk
with Omega Leonidas evolved from Leonidas by gaining power from Delta Dragonoid 2 , Storm
Skyress , Blade Tigrera , Hammer Gorem and Preyas 2 Angelos or Diabols

he can be black

leonidas is the coolest and the strongest bakugan ever!!!

He is your partner and you need him in order to beat the crap out of other brawlers
butts.(He is sooooooooooooooooooo cool and he is also the most powerful bakugan ever!)

Leonidas is a powerful Bakugan born in the Doom Dimension. He comes to Earth and then
becomes your partner when he meets you. At first Leonidas is all about defeating every
single Bakugan to unleash his true power but after a while, he befriends you can becomes
less aggresive. Near the end of the game he evolves into Omega Leonidas by combining
Delta Dragonoid 2, Storm Skyress, Blad Tigrerra, Hammer Gorem, and Preyas 2
Angelos/Diablos's power. With his new power you must use him only to defeat your sinister
rival, Marduk, after you defeat him at the UBT (Ultimate Battle or Bakugan Tournament).

I hope this answer helped you figure out who Leonidas is (also referred to as Leo).