This was more or less answered in the rules, but me and my play partner wanted to be sure.
Based on the wording in the rules, it sounds like the active player may stack the effects of any cards that have identical timing to his or her liking.
For example: Maugan-Ra (Yellow Threat - 5 Cunning) says "At the start of this battle, test Willpower 8. If you fail, you cannot play any Power cards during this battle.
However, if you have the Power card Lightning Reflexes, it's timing is "Play at the start of a Cunning battle." Could the active player prioritize Lightning Reflexes into effect before Maugan-Ra's effect? This makes sense based on the wording of the Timing rules, however I was not sure if enemy effects took priority duing combat.