Kelavtra, Enona's Rebirth

When Kelavtra, Enona's Rebirth enters the battlefield, create X green
1/1 Elf Soldier creature tokens, where X is
equal to the mana spent to cast it.
When an Elf you control dies, exile it instead.
You may cast that spell for as long as it remains
exiled this way. If a token would be exiled this
way, create a green 1/1 Elf Soldier creature token
at the start of your next turn.