Man-At-Arms

Man-At-Arms is Duncan, weapons master of Eternia, adoptive father of Teela, and one of the few who know Prince Adam is He-Man. Man-At-Arms is also a job title he inherited, and one he eventually loses.

It is a post, not a name

Mattel’s Masters of the Universe Classics cardback opens with a sentence that most retellings skip:

REAL NAME: Duncan

For two centuries, the Eternian weapons master and combat instructor to the royal family has been called the “Man-At-Arms.”

Man-At-Arms is an office. Duncan holds it. Others held it before him and, as it turns out, someone holds it after him.

The rest of the card sets out his career. Duncan was trained by the renowned tactician Dekker and came through the Great Unrest as a veteran of it. King Randor then asked him to take the post and to fortify the royal guard with an elite strike force, which Duncan named the Masters of the Universe. The card also makes him a great inventor, and credits him with building an electronic version of the Power Sword for Adam to use until Adam could unite both halves of King Grayskull’s sword. It closes on Duncan and his adopted daughter Teela scouting the borders of Eternia for signs of lurking evil.

Two things there are worth stopping on. Duncan named the Masters of the Universe: the team is his coinage, not a title the universe applied to them. And the electronic Power Sword is a piece of engineering that only exists because Adam could not yet transform, which lines up with the techno vest and built-in force field on He-Man’s own card.

Mattel’s Dekker card tells the succession slightly differently. Dekker was a mercenary from the Dunes of Doom who switched sides during the Great Unrest, became King Miro’s Man-At-Arms, took “a young prodigy named Duncan under his wing”, and then retired to Orkas Island “passing his title and duties to his former apprentice and sidekick”. So Dekker’s card says Dekker handed the post on. Duncan’s card says Randor asked him to take it. Both are official and they are not quite the same event.

Filmation gave him the personal name Duncan late. It is spoken on screen in the 1985 episode “The Problem With Power”, two full seasons into a 130-episode run.

The card where he stops being Duncan

The Classics line released a Snake Man-At-Arms figure, and its bio is the single grimmest thing in the whole cardback set:

REAL NAME: Duncan of the Viper Clan

Exposed to the Serpent’s Ring, Duncan was magically transformed by King Hsss into a Snake Man permanently.

The rest of the card follows that through to the end. Under the spell he uses his genius to build great and horrific machines of war for the Snake Men. He is replaced as Royal Man-At-Arms by Clamp Champ, is forced to fight him, and is mortally wounded in their final duel at the Second Ultimate Battleground, recovering his own humanity for a moment beforehand thanks to a spell cast by his daughter Teela, by then the new Sorceress of Grayskull.

Every part of that is load-bearing. The transformation is permanent, not a temporary curse to be broken in the third act. His inventiveness, the thing that made him useful to the heroes, is turned against them and used to arm the Snake Men. He is replaced. And he dies, in single combat with his own successor, restored to himself for a moment by his adoptive daughter.

Clamp Champ’s card confirms the succession from the other end. Raenius, formerly King Randor’s bodyguard, stepped in as the new royal Man-At-Arms after Duncan was captured and permanently turned. The card is candid that Raenius is not the equal of the man he replaced: he lacks Duncan’s skills as an inventor, and proves himself instead through hand-to-hand combat and weapons knowledge, particularly the techno clamp that gave him his nickname. He leads the Masters of the Universe all the way to the Second Ultimate Battleground.

A small consistency note that matters if you are quoting these cards. The Snake Man-At-Arms card spells the Snake Men leader “King Hsss”, with three s. Evil-Lyn’s card and the Battleground Teela card both spell him “King Hssss”, with four. Neither reading has been photo-verified, so this is a difference within one transcription rather than a proven Mattel inconsistency.

Teela

Duncan’s card calls Teela “his adopted daughter”. Teela’s own card, which we have photographed, calls her “the adoptive daughter of Duncan, the current Man-At-Arms”. The Sorceress card explains how it happened: Teela’Na, the Sorceress, was cloned by Skeletor, saved the resulting child with Man-At-Arms’s help, and gave the baby up to him to raise.

Duncan therefore knows exactly who Teela’s mother is, and does not tell her. He is also one of the very small group who know Adam is He-Man. He spends the Filmation run keeping two secrets from the person he raised, and the series never asks him to account for it. Revelation does, and that is most of what Liam Cunningham’s performance is doing: an older Duncan whose moral authority holds the cast together during He-Man’s absence, framed as a grieving father.

The same voice on both sides

Alan Oppenheimer voiced Man-At-Arms in the Filmation series. He also voiced Skeletor. Both characters are in most episodes, which means the hero’s mentor and the villain trying to kill him are the same performer arguing with himself.

Idris Elba plays Duncan, Man-At-Arms, in the 2026 live-action film.

James Purefoy plays King Randor. Several early listings mixed these two up and the mistake is still circulating. Elba's Duncan is Chief of the Royal Guard, gravely wounded by Trap Jaw in the opening assault and given his rematch in the finale, and he rebuilds Roboto, who is female in this film and played by Kristen Wiig, in the epilogue. The film also gives him a brother, following Mattel rather than inventing: Fisto is named Malcolm and written as Duncan's younger sibling, where Mattel's card makes Malcom the older one.

More on the 2026 Masters of the Universe film

• He-Man
• Teela
• The Sorceress of Castle Grayskull