Karn, Living Legacy

You can use the {C} added by a Powerstone token on anything that isn’t a nonartifact spell. This includes paying costs to activate abilities of both artifact and nonartifact permanents, paying ward costs, and so on.

If you look at one or more cards this way, you must put a card into your hand. You can’t choose not to put one into your hand.

Although all the cards in the Dominaria United set that create Powerstone tokens create a tapped Powerstone token, entering the battlefield tapped isn’t part of the token’s definition. Notably, if you create a token that is a copy of a Powerstone token, the token copy won’t enter the battlefield tapped.