Rionin, Demonized Traitor

When you cast Rionin, destroy all elves in play, then create a 3/1 demon creature token with flying
Rionin's power is equal to the number of elves in all graveyards, and his toughness is equal to the number of demons on the battlefield.
{b/g}{b/g}{t}; Create a 3/1 demon creature token with flying onto the battlefield.