In all chapters you have a hub area where you upgrade your character and can see collected enemies (bestiery)

Example chapter 1 hub area

At first this area is empty. With each bestiery collected you add an enemy.
You need to collect them once. After you collect bestiery entry it will be saved for future runs ( best use is for realmshit mode ).

At the end of the area, there will be a button, when pressed you will release all collected enemies.

Those enemies count as normal, they drop loot, count towards challenges and achievments.

In realmshift mode, if you have full bestiery, you can get a lot of weapon upgrade points and skill points from this area. For maxing out all weapons early on you will need to visit this area 2-3 times ( depends how good you did on a mission )

As for skill points it dropps but not as much as weapon upgrades.

I hope this guide will help you with Realmshift runs.