I really like this card. It's an interesting color pie expansion idea conceptually. Theoretically it's a ritual effect in , but in practice that really holds true against a control deck or whatever. In most cases it functions more like a Gulf Squid / Mana Short.

I suspect the card is a tad underpowered at the moment though.

It's also the opposite of Mana Geyser which sets up a nice contrast between the two colors.

I like it. Not everything needs to be massively powerful, and I can see decks running this as it is.

Blue shouldn't have these kinds of explosive rituals any more. And also the fact that the card often comes down to your opponent tapping out in response seems like a bug rather than a feature.

I'd suggest moving it to red with the following change: "Add to your mana pool for each untapped land target opponent controls as you cast ~."

Wording: Jaws of Stone

It also seems more appropriate for red to punish an opponent's inactivity rather than proactiveness (Citadel of Pain, Stoneshaker Shaman).

Alternatively, you could just give a different reward. "Draw X cards, then discard X cards, where X is equal to the number of untapped land target opponent controls." Really puts the squeeze on your opponent, too.

Either way, though, this should really target. Unless you want it to hit each opponent. Which you might. I mean, have you seen what starts to happen when opponents stop caring about Rhystic Study?

Well, you could make it: Target opponent taps all their lands. They may then untap some of their lands, giving you per land they untap this way.

Same thing, slightly blueyer flavour; and more obviously a mana-short rather than a ritual.