The Ancient Minister (エインシャント卿, Einsyanto Minister) is the primary antagonist for the majority of the Subspace Emissary. He appears to be the field leader of the Subspace Army and controls the R.O.B. Squad and their deployments of Subspace Bombs. He is considered to be a tragic villain (an antagonist who does not truly intend to be a villain), as he truly regretted his actions of bringing the World of Trophies into Subspace under the orders of Tabuu.
 Role in the Subspace Army
 Pre-Subspace Emissary
Ancient Minister was once known as the Master Robot who ruled over the Isle of the Ancients with the rest of the R.O.Bs. Tabuu held the entire island hostage, forcing the Master Robot to follow his orders. The Master Robot, in his own shame, disguised himself and took on the name Ancient Minister.
Tabuu used technology from the Isle of the Ancients to build Subspace Bombs and the Subspace Gunship and began production of the Subspace Bombs on the Isle of the Ancients and the Subspace Gunship. Each Subspace Bomb required two R.O.B. units to be sacrificed for unknown reasons. These units and a number of military specialized units became the R.O.B. Squad. A number of Subspace Bombs and sacrificial R.O.B units were deployed into the world, while the Subspace Bomb Factory was formed on the Isle of the Ancients and protected by most of the R.O.B Squad.
 During the Subspace Emissary
The Ancient Minister is the first real enemy encountered, as the fight between Kirby and Mario seemed to be friendly in nature. The Ancient Minister deploys a Subspace Bomb in the Midair Stadium, assimilating it into Subspace. This first attack was protected by the captured Battleship Halberd. Mario, Kirby and (depending on who the player saved) Princess Peach/Zelda escape. He then attacks a number of different locations with Subspace Bombs. As the story progresses, the Ancient Minister is shown to be saddened by the loss of R.O.B. units, having a number of flashbacks about the lost R.O.B. units.
Every location absorbed into Subspace causes a number of new characters to join a party that fights against the Subspace Army. Eventually, the party enters a large room in the Subspace Bomb Factory with a number of R.O.B. units and Subspace Bombs inside, as well as the Ancient Minister. Ganondorf appears via hologram and orders the R.O.B. units to detonate all the Subspace Bombs at once. The Ancient Minster physically moves them away from the Bombs and orders them not to detonate the bombs. Ganondorf then reaches for a remote and hits a button on it, causing all the R.O.B units eyes to glow red and their motion to become more mechanical. The R.O.B. units, now unresponsive to the Ancient Minister's commands, continue to follow his orders for detonation. The Ancient Minster continues to physically remove the units from the bombs, which leads Ganondorf to order them to attack. The R.O.B. units light the Ancient Minister on fire using lasers and the Ancient Minister destroys the robes that he was wearing, putting out the flames and revealing himself as R.O.B. to the party of heroes, being introduced as R.O.B. He joins the party, who all collectively attempt to remove the R.O.B. units from the Subspace Bombs to no success. Ganondorf orders the Subspace Army to attack the party, which evacuates. The party escapes using the Falcon Flyer, fighting Meta Ridley in the process.
The Isle of the Ancients is engulfed by the bombs and enters Subspace. The Subspace Gunship exits out of it and begins attacking the party, who use various aerial vehicles to fight back and enter Subspace. The Master Robot confronts and is trophified by Tabuu along with the rest of the party, who are all restored by the likes of King Dedede, Ness, Luigi and Kirby. The Master Robot is a playable character for the Great Maze and the final fight with Tabuu, though he is referred to as R.O.B.
 Post-Subspace Emissary
The Master Robot is seen with the thirty four other playable characters, who stand in front of a shore and stare at a large X shaped light in the sky, which was once the Isle of the Ancients. Due to so many bombs being detonated in it at once, the Isle of the Ancients can not escape Subspace and is thus gone for good.
The rest of the R.O.B. units were either on the Isle of the Ancients when it was destroyed, destroyed when the Subspace Bombs were deployed, or destroyed by the heroes when they attacked the Isle (it appears as if only the Master Robot is capable of trophification instead of death), meaning that he is the last R.O.B. remaining.