I know the rule is that you can only use a power or type of card once per check, but I guess I'm not sure how exactly it works.
I'm playing through AD4, and I have Estra's power that allows you to reveal a blessing or spell to reduce damage dealt to her by 5. She encounters the villain, who deals 1d4+1 poison damage to her before she acts. She fails the check to defeat and takes 4 combat damage, and the villain also deals 1d4 poison damage if undefeated.
The way I assumed it works is that I can reduce the Before you act damage, and then I have to choose between reducing the combat or poison damage since they both happen as a result of the same check, but I wanted to make sure so I have it defined for the future.