The bosses on floors 110, 120, and 130 are always Primal. Every 100 floors the boss is instead a Centurion, which is a special unique boss that also always gives File:HeroSoul.png. Note that only the first boss on a given floor can ever be Primal. If you defeat the boss of a floor and then return to fight the boss again, the additional bosses will never be Primal. However, if you encounter a Primal Boss and then leave the floor or get defeated, the boss will still be Primal when you return.