Arachni is a character from the anime Children of the Whales who serves as a member of the Allied Empire and holds the position of Commander of Skyros. Regarding his background, the author of the original work has indicated that he is somewhere in his early thirties. His name is derived from the Greek word for spider, αράχνη.

In terms of personality, Arachni initially presents himself as a very cautious and emotionless individual. However, this demeanor shifts dramatically in combat situations. When he engages in battle against Ouni and others on the floating island of Skyros, he behaves in an arrogant manner. This arrogance proves fragile, as he quickly panics once the tide of battle turns against him. He is also characterized by a strong sense of ambition, which manifests in his willingness to disregard the commands of higher-ranking officers, including a superior named Orca. Regarding his role in the story, his primary function is as an antagonist representing the Allied Empire's forces. His motivations appear to be driven by this ambition and a desire to achieve his own objectives, even if it means going against the chain of command.

Key relationships in his story are primarily defined by his association with the Allied Empire and his direct conflict with Orca, whose orders he ignores. His development within the narrative leads to a specific conclusion, though it differs between adaptations. In the anime, his fate is more ambiguous, but it is presumed that he is sentenced to death by the Allied Empire's council. In the original manga, his fate is definitive; he is killed by Orca after shooting him. Regarding his notable abilities, no information is available.