The Plague was one of the things which caused the downfall of the Aetherii Collective, and presumably many of the other Ancient Empires, in the times of old long before man even stood upright.
There have been two mentions of the Plague, one was from an Aetherii message to the Triarii, which simply talked of the Plague alongside the Darkness. Another was found upon an ancient datachip
"And the seers have foretold
Of decay in the cold
That broke upon walls of flesh
Brothers of old
Felt it's breath scold their souls
And broke upon it's dark command"
What is the Plague?Edit
There have been many theories put forwards by the Argutus towards what it is, and some hold that is may not actually be a disease in the traditional sense but might refer to war or hatred. No one is entirely saw what the Plague actually is.