Polydemons, or Chimera demons, are horrors beyond horrors.
A demon's whole body is "alive" in much the same way a plant's whole body is alive. The head contains the most intelligence, but even a demonic finger holds information and energy far beyond what a human finger could ever hold.
In many ways this doesn't matter very much, because if you blow the head off a demon the rest of the body is unable to sustain itself, and will eventually die.
However an interesting thing happens if a demon eats another demon. Instead of breaking down the matter into pure energy, as they would with human or animal flesh, the "personality" of the consumed demon lingers.
This by itself would not cause much beyond a discrepancy in thoughts, and some erratic behavior, but demon flesh is, by all accounts, MASSIVELY ADDICTIVE to other demons. Once a demon consumes demon flesh, it wants to eat NOTHING ELSE.
As more and more flesh is consumed, power is quickly added, and the personalities increasingly clash and interfere with each other.
Madness occurs rapidly, and then all that is left is a massively strong, massively hungry, demon flesh addicted monstrosity.
All demons must hunt and kill any demon that becomes addicted to demon flesh. Of all the things the angels have weaponized in the past, surely this was their most loathsome.
Remember this always...
-Teachings on Demon biology by the Demon Master Buzhum