Experimentation.

Xander is currently above the castle scanning the fortress from every direction from the shadow realm. She is also sharing her sight with Aeternus who is performing experiments within the castle. Aeternus is in a large room adjoined with many cells for experimental subjects. Some of the cells contain his subjects, mid-rank demons.

The large room also contains many mid-rank demons in various stages of evolution or fighting. The ones that are fighting are at each other's throats as if they are crazed. He sat on a pillar while he watched everything going on. Occasionally he would make some changes to the developments by releasing some dust that resemble fireflies into the air. 

These fireflies are then absorbed by the demons. Some instantly start to evolve while some begin to fight each other. Some of those evolving fail and release fireflies which he takes and examines. The ones fighting kill their opponents and absorb the fireflies from the body of their opponents.