Glowform Cavern

Glowform Cavern enters the battlefield tapped.
{g/u}{g/u}, {t}, Tap X untapped creatures you control:
Reveal the top X cards of your library. You may
put a card from among them with mana value X
or less into your hand. Shuffle.
{t}: Add {u} or {g}.
It hums with an eerie luminescence.