Jeleva, Nephalia's Scourge

Jeleva, Nephalia's Scourge
{1}{U}{B}{R}

Legendary Creature - Vampire Wizard | Power/Toughness: 1 / 3 (CMC 4)
Flying
When Jeleva, Nephalia's Scourge enters the battlefield, each player exiles the top X cards of their library, where X is the amount of mana spent to cast Jeleva.
Whenever Jeleva attacks, you may cast an instant or sorcery spell from among cards exiled with Jeleva without paying its mana cost.