Devils, or species belonging to the Diavolos class, are considered the most dangerous and violent species that the FLIPSIDE has to offer, representing one of it’s biggest threats to date. All Devils should be considered hostile and should never be voluntarily engaged.
As a group, Devils share little to no similarity with each other. No two Devil species are alike, with the differences being so extreme no sane taxonomist would even attempt to classify them on the same branch of life, or even on a branch of life at all.
Despite this, Devil biology does obey some common rules. All¹ Devils are blind, despite some of them seemingly possessing eyes. Devils leave no corpse behind, with any and all remains disintegrating into a red dust upon death or injury, in the case of lost limbs, with the process being so efficient they don’t leave behind any smell. Devils do not age after reaching species maturity. Devils have specialised organs which allows them to sense and metabolise the fear of other species, as beings experiencing fear in the immediate vicinity of a Devil will invariably increases the reflexes, senses, speed and strength of said Devil. This extends to all species capable of feeling fear and that secrete a hormone to regulate it (eg. cortisol and corticosterone have the same effect on a Devil, despite different structure and origin). Along with this, Devils can use blood to heal themselves. This is because of the high concentration of Anima naturally found in fresh blood, which Devils process to heal almost instantly upon consumption.
Their nature is a result of their close link to Anima, as Devils themselves are entirely Anima-based entities. One of the best indicators of Devil activity is the local Anima level, each individual Devil creating a noticeable sink effect compared to other lifeforms. A visual indicator of this effect is Tar, which can be used to determine how many or how active the Devil in an area is.
¹ This rule is bypassed by some species by reworking parts of their biology into somewhat functional eyes, although true eyes are still absent.