Mana Web.

[Evenpence]

I think I may have found a new Stax card.

Mana Web
3
Artifact
Whenever a land an opponent controls is tapped for mana, tap all lands that player controls that can produce any type of mana that land could produce.

Does this work the way I think it works?

Let's say my opponent controls (all untapped) a Volcanic Island, an Underground Sea, an Island, and a Fetchland.

If he taps the Underground Sea, everything will become tapped except for the Fetchland, and he will not be able to get the mana from the Island or the Volcanic Island, correct?

[Mr. Nightmare]

He can still tap out for mana responding to each Mana Web trigger.  He has to use all of his mana during a single phase, and plan very carefully which color mana to add to his pool, though.

[Evenpence]

That's gay.

Okay, thanks.