Masters Edition III

Mana Vortex

When you cast Mana Vortex, you may sacrifice a land. If you don't, counter Mana Vortex.
At the beginning of each player's upkeep, that player sacrifices a land.
When there are no lands on the battlefield, sacrifice Mana Vortex.

When you cast this spell, counter it unless you sacrifice a land.
At the beginning of each player's upkeep, that player sacrifices a land of their choice.
When there are no lands on the battlefield, sacrifice this enchantment.

The Dark

Each player who controls land sacrifices one land during his or her upkeep. If at any time there are no lands in play, Mana Vortex is destroyed. If you do not sacrifice a land when Mana Vortex is cast, Mana Vortex is countered.