Let me break this down for you since I've tested divine intervention extensively. The ability triggers with specific combat-focused options and while it's incredibly powerful, it doesn't actually branch the story in meaningful ways. When you activate it you'll get four distinct choices - massive radiant damage which is great for tough encounters, full party restoration that can save a dire situation, a legendary weapon drop, or resource generation for sustained fights. The key timing for using it is during major combat sequences, especially if you're struggling with shadowheart's questline battles but interestingly it won't change how those story beats play out.

While some players have tried using it creatively like attempting to save certain characters or alter crucial moments, the ability is strictly designed for tactical advantage rather than narrative impact. Your best window for maximum value is during those really challenging fights where you need that emergency button, just remember you only get one shot with it so timing is absolutely crucial. The follow-up effects might help you survive encounters that feel story-critical but the actual plot developments and endings stay locked to your dialogue choices and major story decisions regardless of how you use this ability.