Rak'Utai, Sultai Junglekiller

Forestwalk, double strike (This creature deals both first-strike and regular combat damage.)
Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Rak'Utai enters the battlefield with X +1/+1 counters on it.
Exploit (When this creature enters the battlefield, you may sacrifice a creature.)
When Rak'Utai exploits a creature, Rak'utai get +1/+1 and have haste until end of turn.
"I am the so called Sultai Junglekiller."