Tarot Rings King

Benedict Lightwood, a notorious victim of the disease.

Demon pox, also known as astriola, is a rare but debilitating disease that affects Shadowhunters and is caused by sexual contact with demons.


The first signs of demon pox are a shield-shaped rash on the back of the sufferer, which then spreads over the body, creating fissures in the skin. From this point, the afflicted Shadowhunter will deteriorate physically, experiencing fever, chills, nausea, oozing sores, non-oozing sores, buboes, a film of black over the eyes, hair ejection, skin discoloration, swelling, and other similar signs of distress. The demon pox would then aggravate and may lead to insanity. In time, the sores and fissures cover the skin of the victim entirely, and they form a dark chrysalis within which the victim transforms, painfully and over the course of several weeks, into a demon himself. Once the demon emerges from the chrysalis, the previously existing person is in effect deceased, and the only end to the torment is to kill the demon.[1]

In earlier times, astriola was invariably lethal, and not much could be done for the sufferer but to make him comfortable and to remove him from innocents who might be harmed when his full demonic alteration took place. The progress of the disease could be slowed but not stopped, and in many cases the victim would choose not to be treated, since by and large treatment would only prolong his agony. Today, there exist reliable cures that can clear up demon pox in its early stages, and the illness now causes few fatalities. It can, however, still be incurable if the sufferer reaches a certain stage of demonification before being treated. In addition, a fairly serious stigma is still associated with the disease, and its presence is considered sufficient evidence for the violation of the Law against consorting with demons. Thus those who are treated for demon pox today often receive this treatment while in the prisons of the Silent City.[1]

Mundanes are immune to the disease, as demon pox is assumed to be caused by the interaction of demon poisons with the angelic nature of Shadowhunters.[1]

Known victims

  • Benedict Lightwood - Benedict's condition was severe enough that he needed the medication supplied to him by Axel Mortmain. This failed and he eventually turned into a gigantic worm.
  • Barbara Pangborn - contracted the pox from her husband, Benedict; she committed suicide out of shame for contracting the disease from her husband.


Will Herondale was shown to have had an immense interest in demon pox and had always been passionate about proving its existence. When it was proven to be a real disease, Will is ecstatic and made up a song about it.[2] He later taught the song to his children and grandchildren.

“Demon pox, oh, demon pox,
Just how is it acquired?
One must go down to the bad part of town
Until one is very tired.
Demon pox, oh, demon pox
I had it all along—
No, not the pox, you foolish blocks,
I mean this very song—
For I was right, and you were wrong!”

Will also made up a song to cheer up a sick Jem Carstairs.[3]

“Forsooth, I no longer toil in vain,
To prove that demon pox warps the brain.
So though 'tis pity, it's not in vain
That the pox-ridden worm was slain:
For to believe in me, you all must deign.”


  • Demon pox is based on syphilis.[4]
  • Not all demons give demon pox; or at least, not every sexual contact with a demon will result in contracting the disease.[5]