Yikes!!

"nonmana ability", please. And that'd still need to cost about 5.

Good catch on the non-mana wording.

I'd like to test it cheaper than 5. I'd started it at three, but I really would like to see the card go from "nuisance" to "official pain in the ass" when jumping from a single copy on the board to multiples. Cost it too high and nobody wants it, as it hits too late to matter.

This is official pain in the ass with ONE copy. It's too cheap at uncommon and quite likely unfun.

I really don't think it's as hard to play around as it looks, at least with a single copy in play; don't play land before combat, and hold off on pre-combat spells whenever possible. Outside of aggro, most decks can do this. The activated abilities part is the hardest to play around, though plenty of decks won't even need to worry much at all.

The card, by itself, will make your opponent have to do some tiptoeing. In multiples, it will be a brutal burden. But that's really what control is about.

None the less, I've nudged the CC and made it rare.

I don't know; this still seems unfun.

Any deck that has to live in the main phase basically has a new tax added to it; could be a +1, could be the creature you left to block is now tapped, could be the artifact you wanted to use.

And it triggers every time. Essentially, this says; play instants on my turn only or epic slowdown and what blue deck isn't going to love this?

You: play X Me: tap that land, Mana Leak, oh you only have 2 left? Bummer. Don't mind me while I just sit tight on your turn though.

You: instant during combat? Me: HAHAHAHA, yeah that'll never resolve and cripple your 2nd main phase.

Possible alternate: Whenever an opponent has a permanent come into play, tap target permanent.

Still brutal, but only works when something resolves and can target the thing that just came into play.