Rivermouth, the Winding Runnel

Rivermouth, the Winding Runnel enters the battlefield tapped unless you choose two--
Pay 2 life, discard a card, or sacrifice a creature.
{t}: Add {b}, {g}, or {u} to your mana pool.
"The village was designed to hide from aerial assault; buildings and pathways were placed carefully
underneath the canopy. Only when I landed did
I notice the sign of civilization there." ~Demetrius