Before a long battle, there are a lot of attempts to roll the die and subdue the Elder brain.
What happens if we roll a critical success on every die using the safe scam method? Will this skip the entire final battle and give us a secret ending?
There is a video with every non secret ending + Raphael's on YouTube. Including this one. You do need to subdue it to reach two of them, but I can't recall what that lets you skip. It's really the same ending, just slightly different for Durge.
About 1h 30 minutes long. Get Firefox and install a quick YouTube ad blocker if you haven't done so before. Or watch the ads.
Just keep in mind that the main purpose of subduing it is to get the evil ending. You can also have the Emperor do the rolls for you, who will automatically succeed and, remarkably, not stab you in the back. If there is any backstabbing, it will be from your end. Arguably part of another Durge ending.
If you control the brain, not the prince or emperor, you get access to the default evil ending. It's not exactly secret.
