RulingRules Reference 1.7

If a character with the Power Stone is dealt 3 or more damage but does not take 3 or more damage due to damage…

Question

If a character with the Power Stone is dealt 3 or more damage but does not take 3 or more damage due to damage prevention, does the attacker get the Power Stone attached to them?

Answer

Yes. Damage prevention does not reduce the amount of damage dealt. Note that a hero making a basic defense reduces the amount of damage dealt by that hero’s DEF, so defending an attack can prevent the Power Stone from being taken. R ENCE

— Rules Reference 1.7