Playing in the quest mode on the Legendary Difficulty, the main power is that all undead roll 2d4 extra to beat. Skinsaw Man also rolls 1d4 to add to the check if your character is at the location with no other heroes.
In my quest game, it will roll the 2d4 for the scenario power, but hangs on the 1d4 for the hero being alone. It just sits there, and I can't get it to roll.