Other monsters

"What is it?" I asked after seeing that awkward look on the gnome's face.

The gnome seemed to hesitate to show what was making it feel awkward, but it did it in the end.

The gnome went over to the machine that had the tablet and opened up a compartment in that machine before reaching in to pull out something for us to look at.

He held that thing up in front of him for us to see.

It was a crystal, but it seemed to be completely colourless. It seemed like whatever had been inside of the crystal had been completely drained, which was why it had lost all colour like this.

But we recognized this crystal.

This was something that anyone that dived into the dungeon recognized since it was one of the most common things that dropped from the monsters of the dungeon. 

This was a monster core that humans now used as a source of clean energy.

It seemed that the gnomes had figured out a way to use this monster core as clean energy as well.