Bolas's Citadel

You may look at the top card of your library
any time.
You may play lands and cast spells from
the top of your library. If you cast a spell
this way, pay life equal to its converted
mana cost rather than pay its mana cost.
{t}, Sacrifice ten nonland permanents:
Each opponent loses 10 life.

Roanapura, the city of the Black Lagoon