Crystals

Crystals (also sometimes translated or referred to as gems, magic stones, demon stones, and cores) are a crystallized source of power residing within monsters. Destroying them means killing the monster. In the web novel and light novel, animals do not have crystals. The stronger the monster, the better the crystal, and the more crystal points it gives to Teacher.

How they are used: getting materials from a monster will get a buff for example a Poison Fang Rat, using the materials on some armor would give it Poison Resistance while crafting a weapon with it will give it Poison Fang, but using the Poison Fang Rat Crystal, you get more Poison Resistance and Advanced Poison Fang instead. using different materials and crystals would yield a lesser buff, but matching certain materials with their corresponding crystal. you would get a greater effect.

When absorbed
So far, Teacher is the only one capable of absorbing crystals, and therefore the only one able to taste them. Rather than different flavors, it is more akin to the quality of magic deciding the taste.

Demonkin
The crystals of the demonkin have a vaguely spicy taste.