Should be something you need to deal with immediately.

Maybe non-land permanent? Not having the mana for removal would make this hard to deal with.

Good call.

To me it seems a bit nonsensical that you could throw this basically into any black deck and get rid of artifact and enchantment rather easily.

That, and this is just sickeningly powerful. While I'm definitely not a fan of artifacts (colorless cards) destroying permanents left and right, at least those effects have usually been kept behind + mana investments; Argentum Armor, Universal Solvent, etc.

Yeah, this is very very cheap for its effect. This is repeatable destruction at (and possibly at if you can find a way to keep a creature alive).

Another apt comparison would be Lux Cannon. While it takes less than mana to get going, it takes four rounds (three tap rounds + the actual payoff round) before it can blast anything and then it needs to start recharging again.

Yes, it can also Stone Rain, but the likelihood of you doing that with it is like less than 10 % (at least from my experience). That usually means you are making someone's mana screw worse, that is, you are already on the winning side so it doesn't really even matter that much.

Oh yeah. This is way too overpowered. You can also compare to Argentum Armor. This version of the card is kind of a placeholder until I figure out a good design.