Quote from questbook:
At the start of the overlord turn, is Skarn is unconcsious. he recovers HEARTS equal to half of his total Heatth and is Stunned .
OL card Ward of Peace:
Play this card on 1 monster group during your turn and keep it in your play area.
Discard all conditions from this monster group.
Each monster in this group is immune to all conditions. Discard this card if a monster in this group spends a surge result during an attack
And golden rule from new Errata:
The first bullet point should read, “Some cards and abilities come in direct conflict with the rules found in this rulebook. Cards and abilities take precedence over the rules in this rulebook. Furthermore, many quest rules listed in the Quest Guides come in direct conflict with cards, abilities, and the rules found in this rulebook. The quest rules listed in the Quest Guides take precedence over cards, abilities, and the rulebook.”
So the question is: Can OL use Ward of Peace to prevent Skarn from getting that stun condition?
For me that depends on the way you treat "immunity" to conditions.