Abasdarhon's Castle

Let's see the map.

Adaptation | Diseases, poisons, and bleeding do not affect the character | – 17%

So, there is no generation process, except for discussing this with the hero? What if additional bonuses are dropped from cards? What if they are mutually exclusive?

The generation is not much different from the generation of a regular character, only slightly stronger than others. You can create a special ability, within reasonable limits, of course.
If bonuses that do not contradict the demon are dropped, they will work.
If they are mutually exclusive, there will be a coin flip.