My sorcerer encountered the boss, so I was given the option to temporarily close other locations. My druid successfully closed the woods, and my fighter & bard were in the Mill, so I chose my fighter to encounter a monster to close it, which turned out to be a Yeth Hound. Both the fighter and bard failed the Wisdom roll, but then the sorcerer was the one who actually encountered the Yeth Hound, not the fighter. She failed the encounter, and discarded both her cards.
The boss was the one who makes someone at the location summon a Wrathful Sinspawn henchman, but that didn't happen, instead the boss card just stayed there as if it was being encountered and nothing happened. I had to forfeit to continue doing anything.