Sira's Hollow

Sira's Hollow enters the battlefield tapped.
{t}: Add {g} or {b} to your mana pool.
{3}, {t}: Put a +1/+1 counter on each creature that entered the battlefield this turn under your control. If that creature is a Werewolf, it gets two +1/+1 counters instead.
Where the howls drown out the bells.