If it's ONLY in certain scenarios then it's kind of similar to the Chaos Ascendant rules from Glottkin, except with the Magic Boost there'd be incentive for BOTH sides to agree to playing those scenario rules. With the Chaos Ascendant rules in Glottkin there's really no reason why you should agree to playing those rules as they benefit purely the chaos player and chaos are meaty enough as it is.
There's those who can play Warhammer. For those who can't, don't worry, Chaos has got your back.
There's those who can play Warhammer. For those who can't, don't worry, Chaos has got your back.