Armaros spent a millennium trapped in a Pyxis kept in the London Institute, before it was stolen by Nate Gray for Axel Mortmain. Armaros was then freed by Mortmain and bound to an automaton to become part of his Shadowhunter-destroying armies. With its life tuned to Mortmain's, it was obliterated, along with the other demonic automatons, when Tessa Gray Changed into the angel Ithuriel and killed Mortmain.
The name Armaros means "cursed one" or "accursed one" and is likely a Greek alteration of Armoni, possibly an Aramaic name.
- According to him, he fought Jonathan Shadowhunter on the plains of Brocelind. It is possible that Armaros was among the swarm of demons that attacked Jonathan, David, and Abigail the day Raziel made them Nephilim.
- As per the biblical Book of Enoch, Armaros was the eleventh among the twenty leaders of a group of 200 fallen angels called "Watchers".
- Clockwork Princess (first and only appearance)