Nulls, also known as Devourers, Void Walkers and "Those" People, are a newly discovered sub-species of humans.
As we all know (or at least i hope you do), mana is the vital energy that exists within all living (and unliving) beings in the world, be they man, god, monster, animal or plant. However, that is not the case with Nulls.
In recent studies, it was confirmed that Nulls possess no mana of their own, not one bit. They are like a statue that can walk around, breath, eat, drink and sleep, but isn't, at least by this meaning, alive. The fact that even undead and living objects possess mana (monster mana in this case) really says something about their condition.
But that is not all about them, for you see, not only do they not possess their own mana, they are also, in a crude terminology, mana black holes. Let me give an example of what this means.
Whenever a Null does, well, anything, they will exude an aura that is invisible to the naked eye that absorbs all the mana around them, human, monster, all alike. This happens just by them existing, so most of them aren't even aware that they affect the environment in this way.
Because of this condition, Nulls can't be affected by mana at all, as they will simply "eat" whatever spell you cast at them, nullifying it in its entirety. And because they have no mana of their own, they are not affected by mamono mana in any way, hance, a Null cannot become an Incubus.
However, they can become the beings known as Heros. In fact, one of the Order's newest Hero is a Null himself, and because of this, the Order is managing to gain some footing in their war against monsterkind for once.
Lastly, because of their unnatural condition, Nulls can make others around themselves feel uncomfortable in their presence, with how much varying from species to species. Normal, everyday humans might not feel a thing around them as they are not well trained in magic, whereas mages will "feel" their unnaturalness, and monsters out right fear them, and avoid being near them if they can. The latter varies from monster to monster, the more civilized ones might just leave their current vicinity when a Null is nearby, whereas a wild monster might have their "Fight or Flight'' instinct activated, and trust me, they will fight if they can't flight.
This concludes the introduction to these "new" humans. What makes some of them to be born this way is still unknown, but their potential destructive capabilities are well known and documented, as the Order did not waste any time in using Nulls in their crusade against monsterkind.
Author's notes: Nulls are a sub-race of humanity that exists in my universe and I thought of bringing them to the MGE universe. Next time I'll make all the abilities and skills a trained Null can learn and use against spellcasters and other enemies in general, then I think I'll make the Daemons from 40k. See you all there!