Drain Power

Target player activates a mana ability of each land they control. Then that player loses all unspent mana and you add the mana lost this way.

30th Anniversary Edition

Masters Edition IV

Target player activates a mana ability of each land he or she controls, then empties his or her mana pool. Add mana to your mana pool equal to the type and amount emptied from that player's mana pool this way.

Fifth Edition

Target player draws all mana from all lands he or she controls. Put all mana from that player's mana pool into yours.

Fourth Edition Foreign Black Border

If a land can draw a variable amount of mana, the target player (not the player of this spell) chooses how much to draw.

This card forces the target player to draw mana from lands if they are untapped, but that player can choose how to draw the mana if a land they control has multiple mana abilities, or mana abilities with choices.

Your opponent may use instants and abilities of permanents in response to this spell before you get the mana.

A mana ability is an ability that (1) isn't a loyalty ability, (2) doesn't target, and (3) could add mana when it resolves.