Eldomain is a Fleet Commander Colonel in the Alfres Militia, an Afressian from the homeworld Afres. He holds the military rank of Colonel and serves as a soldier for the Afressian faction. His appearance features blue hair cut to neck length and black eyes; he is designated an adult.

Personality-wise, Eldomain exhibits overconfidence, cowardice, and dishonorable tactics. He remains loyal to Queen Baraluda, ruler of Afres, despite her later disapproval. His actions include terrorizing civilians in saloons and attacking unprovoked cargo ships. He adorns his command ship with a Jolly Roger pirate insignia, a symbol Emeraldas claims exclusively for her vessel and Captain Harlock's Arcadia. He ignores her direct order to remove it, using the emblem as bait to lure her into conflict.

His narrative centers on repeated defeats by Emeraldas. After an initial defeat where his forces retreat following an attack on a freighter saved by Emeraldas, he devises a trap using a fake distress signal from a ship bearing the forbidden insignia. This successfully draws Emeraldas away, allowing him to capture hostages on Daibaran, including Hiroshi Umino. He attempts to leverage these hostages to force Emeraldas's surrender or destruction, threatening their lives if she resists.

The hostages escape through collective action and a diversion caused by a stray cat, enabling Hiroshi to disable guards and alert Emeraldas. Eldomain's subsequent deployment of his flagship's primary weapon, the Domain Gun, fails to damage Emeraldas's vessel. As his fleet is destroyed in the counterattack, he attempts to flee. Queen Baraluda intercepts and kills him with a beam weapon, condemning his cowardice and dishonorable tactics as unforgivable.