Essence Keeper

Level up {1} ({1}: Put a level counter on this. [1/1]
Level up only as a sorcery.)
———{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}
Level 2-3> Whenever another creature enters
the battlefield under your control, you [2/2]
gain 1 life.
{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}{line}
Level 4+> Whenever another creature enters
the battlefield, you gain 1 life.