Nurgle's Rot is one of the most malicious and foul diseases to exist in the Warhammer 40K universe and was spawned by the Chaos God Nurgle, from whence it has earned its name - "Papa Nurgle" continually seeks to outdo this creation but so far Nurgle's Rot has remained his most powerful creation and an apocalyptic plague feared across creation.
Nurgle's Rot does not kill its host quickly; rather, it slowly mutates the victim into a bloated living corpse teeming with unspeakable torment and despair.
Their blood curdles in their veins, their eyes grow together into a single globulous orb, and a horn sprouts from their head.
The illness does not merely affect the body, however -- it painfully corrupts the diseased mortal's soul to the point where the victim has to either end their own life or fully embrace the ways of Grandfather Nurgle.
Only when death finally claims the victim will they realise the true blessing that has been visited upon them, as their soul is reborn in Nurgle's Garden within the Realm of Chaos in the immortal shape of a new Plaguebearer.