The Darkness is an malevolent entity of unknown power. It is currently 'trapped' on the fringes of space, but being a shifting being, it is possible it might one day escape to wreak havoc once more
It is currently unknown how old the Darkness is, or whether it is ageless. Likewise, it is unknown if it is some form of god like Faust, or some alien entity. What is known is that it rarely embodies it's self in physical space as it needs to gain a lot of energy to do so, and when it does it takes the form of a pitch black form that is permenantly changing shape
This is the entity that is responsible for the destruction of the Aetherii and possibly even Psionics that came before then. As such, it indirectly resulted in the evolution of the Triarii and thus has had a profound effect on the galazy with none even realising it
Very little has been seen of the Darkness power. What has been seen is that it can take over the minds of any psionic after launching an attack on them, and locates them by searching out their signals once they have used their ability. It was powerful enough to destroy the Aetherii, which causes reason to worry, but does not yet pose a threat to any race aside those with Psionics due to the Triarii attempts to hold it back and contain it. Indeed, with the new awakening of a dormant 'Gift' inside the Triarii, it is having a hard time keeping ground and may once again be ousted from the universe.