Probably horirbly worded - riff on Power Artifact obviously, but also intended to be usable to make, say, prodigal sorcerer less useful.

­Training Grounds

but also intended to be usable to make, say, prodigal sorcerer less useful.

I don't see how. I think you're intending to force Prodigal Sorcerer players to pay at least for their activation... but I don't think the card does that. It only talks about reducing abilities, then tells you there's a maximum that it can be reduced.

Even if this is your intention, You could easily shave a off the casting cost. Heck, you could print a card that says:

"As long as ~ is enchanting a creature you control, activated abilities on that creature are reduced by . As long as ~ is enchanting a creature you don't control, its controller cannot activate abilities on that creature."

...and it would still be fair at .

I said what I wanted it to do; and felt it interesting. That the wording doesn't work doesn't surprise me; that it's underpowered is probably ok. It seems something that shouldn't be splashable, and situational kinda useful.