Biomass

Biomass in the context of the world has a dual meaning and implication.

The monsters themselves defeat other monsters or humans and consume their flesh, from there they gain points in Biomass depending on the tier of the monster relative to themselves. These points can be used to increase or improve the monsters own mutations thus giving them an edge against other monsters (ie. a monster improving its eyes or muscles). The mass of flesh itself is not dormant in the monsters stomach until they decide to use the points but remains present as a sort of energy they can utilize for their own growth even after digestion of the original flesh( i.e a hungry monster that hasn't eaten in a while could still have some Biomass saved up).

In contrast to the monsters utility of Biomass as energy for mutations, when humans talk about Biomass they are simply referring to the flesh of an actual monster. If a human was to consume this Biomass they would take on the properties and some appearance of the consumed monster. The individual in question will also fall to the base instincts of a monster wanting to show off its strength against other monsters, controlling this instinct is key to long term survival. Casual or even rare consumption of monster flesh by humans is taboo and never seen on the surface. It has so far been used by the Legion on captured inmates and convicts to gain access to a fighting force that can withstand the mana of the lower levels. It is unknown whether the consumption of Biomass by other sapient races has the same effect as it does to humans.