These are the parts where the goal is to speed to the end of the level, acquire the emerald / free the animals, and there's a horde of baddies in your way ready to stop you. (monstervine.com)
As for the enemies they activate when the number of black dice on the threat track is equal to or higher than the number of baddies in play. (wolfsgamingblog.com)
The basic idea is that you accept a bounty, enter a multi-level, rouge - lite dungeon and progress through each area by battling rooms full of baddies with special abilities, area effect attacks, shields, and other modifiers that you have to strategize to defeat. (ludonarrativeassonance.com)