Marble Diamond

This enters the battlefield tapped unless you've completed the Undercity Dungeon.

{t} Roll a D20, if it's an odd number sacrifice
this artifact, if it's even add {w}{w}{w} to your
mana pool if you completed the Undercity Dungeon or you have the Initiative otherwise
you must Take The Initiative instead. Anyone
. may pay {w} to take control if sacrificed.