Sorry for this newbie question...
I have 6 characters in play and 3 of them are noble. Then my opponen play Wildfire Assault and I play The Power of Blood.
Can I choose my 3 non-noble characters and in this way "save" them because I can“t kill the noble ones? (The passive effect resolves before the "when revealed")
(3.15) Targetting and Immunity
A card cannot be chosen as a target of effects to which it is immune.
(4.3) The word "cannot"
If an effect has the word "cannot" in its description, then it is an absolute: That effect may not be overridden by other effects.
A character that cannot be killed/saved/etc. may not be chosen for that effect.
Wildfire Assault
When revealed, each player chooses up to 3 of his or her characters. All characters not chosen are killed (cannot be saved).
The Power of Blood
Noble characters cannot be killed.