Mana Short (7ED)

Instant

Tap all lands target player controls and that player loses all unspent mana.

"Remove their power, and their will to fight will follow."
—Tolarian wizard
Greg Staples
86/350
uuid: dd425fd6-d097-5a38-be01-6b29ed30b92a

2004-10-04:
It even taps lands that do not produce mana.
2004-10-04:
Since this is an instant, your opponent may use instants in response to the casting of this spell. Note that such spells and abilities will be resolved before the mana pool is emptied by the Mana Short. This makes it useless as a countermeasure for spells. To use it effectively, you need to use it during Upkeep and even then it will not prevent the use of instant spells and abilities.
2004-10-04:
If you play Mana Short in response to a spell, it will have no effect on that spell since the mana has already been paid.