Creakwood Assassin

Landfall- Whenever a land enters the battlefield under your control, put a -1-1 counter of Creakwood Assassin.
Whenever a -1-1 counter is placed on Creakwood Assassin, target creature gains Bloodrain. (Until end of turn, put -1-1 counters on target creature equal to it's power).
Whenever Creakwood Assassin dies, put it on the top of your library.
{t}: You gain one life and target opponent loses one life.