When Obsidian Aqueduct enters the battlefield, sacrifice it unless you pay .
: Add to your mana pool. Return Obsidian Aqueduct to its owner's hand.
: Obsidian Aqueduct becomes a 2/2 black Zombie creature until end of turn. It's still a land.
.
: Add 
to your mana pool. Return Obsidian Aqueduct to its owner's hand.
: Obsidian Aqueduct becomes a 2/2 black Zombie creature until end of turn. It's still a land.
