this is cool adding to set skeleton

Beautiful flavor

Any way we could make a cost or limitation based on the cost of the creature? Equipment is generally harder to remove than creatures and you could be attacking with Possibility Titan on turn 5.

Possibly? There isn't an X cost equip cost that I am aware of so any wording we do is pretty much new ground.

That said, I think an 8 mana investment is "fair enough" if we have more constructed viable bounce/artifact/instant speed removal. As is, we actually have a number of answers to early Harness. Further, Titan is really only good when you have existing creatures, not on new creatures as much, so dealing with those before they grow up seems reasonable.

In limited, that's seems pretty much a dream to actually have happen. I'm not sure how much we need to worry about this.

All other creatures you control are copies of the equipped creature. seems cleaner