As a GM, I use some revenants for my campaign. Those revenants all have class ability and 2 are spell casters (an abjuration mage and alchemist artificer). The "problem" (it's not a problem, but an "and what if they do that?") is that they can use the `Protection from Energy` spell, so they can have fire resistance.

My question is: What happend if they gain fire resistance (or radiant resistance)?
Do you think they loose their regeneration weakness (that don't work if fire damage were dealt)?