The helmed horror was introduced to the D&D game in the second edition of Advanced Dungeons & Dragons.
Advanced Dungeons & Dragons 2nd edition (1989-1999)
The helmed horror along with the battle horror appears first for the Forgotten Realms campaign setting in the module Halls of the High King (1990), by Ed Greenwood, then in the revised Forgotten Realms Campaign Setting (1993), and was later reprinted in the Monstrous Compendium Annual Volume One (1994).
Dungeons & Dragons 3.0 edition (2000-2002)
The battle horror appears again in Dragon #302 (December 2002).
Dungeons & Dragons 3.5 edition (2003-2007)
Dungeons & Dragons 4th edition (2008-2014)
Dungeons & Dragons 5th edition (2014-)
The helmed horror is an ancient construct that resembles an animated suit of plate mail.
- Greenwood, Ed. Halls of the High King (TSR, 1990)
- Greenwood, Ed. Forgotten Realms Campaign Setting (TSR, 1993)
- Wyatt, James, and Rob Heinsoo. Monstrous Compendium: Monsters of Faerûn (Wizards of the Coast, 2001)
- Baker, Richard, Ed Bonny, and Travis Stout. Lost Empires of Faerûn (Wizards of the Coast, 2005)
- Mearls, Mike, Stephen Schubert, and James Wyatt. Monster Manual (Wizards of the Coast, 2008)
- Mike Mearls, Jeremy Crawford, and Christopher Perkins. Monster Manual (Wizards of the Coast, 2014)