Wow. Last time this was printed, it was rare (Voidslime). Countering triggered abilities has only ever been rare (Stifle, Trickbind). But that said, it doesn't seem like it'd have to be. I suspect this would be more natural as an uncommon though.

Would it help if it was "activated ability"? The intention is to provide an answer to Chargeup abilities.

Hmm, Squelch indicates not (unless the existence of Chargeup mandates it).

I think most people would understand countering an activated ability which feels like a spell; the risk is whether there are enough activated abilities where it's not intuitively clear whether this applies or not, and I don't know if that's the case or not. (I do like the feel of chargecast, although I hope getting a spell potentially for free won't be a problem.)

­Squelch also points out you need more reminder text: "(Mana abilities can't be targeted.)"

Changed to activated abils and added reminder text.

Playtest indicated this was a bit weak at 3; would 2 be too strong with abilities in there as well as spells?

I think I'd expect either for Chargecast Cancel, or for Chargecast Cancel+Trickbind.

Perhaps there's an argument for making this Cancel, reducing the number of Chargeups at common, and having a Squelch or Voidslime at uncommon where the weight of activated abilities would be greater.

I think making this would be the right way to go, makes it more useful in decks not going the charge counter path (whilst still inferior to Cancel).

Updated as part of complexity-reducing chargecast cull. Was 3UU Chargecast counterspell/abil.