Persistent Marshstalker (Bloomburrow)

Creature Ñ Rat Berserker - This creature gets +1/+0 for each other Rat you control.
Threshold Ñ Whenever you attack with one or more Rats, if there are seven or more cards in your graveyard, you may pay {2}{B}. If you do, return this card from your graveyard to the battlefield tapped and attacking.