Dorothy Catalonia is a complex figure from the After Colony timeline, known for her sharp intellect, aristocratic bearing, and controversial philosophy that places her in direct opposition to the era's prevailing pacifist ideals. She is introduced as a student at a school in the Sanc Kingdom run by Relena Peacecraft, but this is a cover for her true mission as a spy for the Romefeller Foundation, a powerful Earth-based military-industrial organization. Her lineage is central to her identity; she is the granddaughter of Duke Dermail, the leader of Romefeller, and the daughter of General Catalonia, a former head of the organization OZ. This background places her at the very heart of the series' political conflicts.

Personality-wise, Dorothy is often seen as the ideological antithesis of Relena. Where Relena champions total pacifism and the complete renunciation of war, Dorothy vocally argues that conflict is an innate and essential part of human nature, something that will never disappear. She speaks with eloquence and a chilling enthusiasm about the beauty and integrity that war brings out in humanity. This belligerent stance, however, is later revealed to be a carefully constructed facade. Deep within, Dorothy is a traumatized individual who despises war for having taken her father's life. Her true, secret motivation is not to glorify battle but to create a conflict so terrible and tragic that all of humanity would be irrevocably scarred and turned away from war forever. She is quick-witted, a master of negotiation capable of manipulating the aged leaders of the Romefeller Foundation, and possesses a fierce, proud streak that prevents her from ever showing weakness, such as crying in public.

Dorothy's role in the story evolves significantly. She first acts as a spy and provocateur within the Sanc Kingdom, pushing Relena to confront the limits of her pacifism. When the kingdom falls, she helps maneuver Relena into becoming the figurehead Queen of the World for Romefeller. Later, she journeys into space and joins the White Fang, a rebel colony army led by Zechs Merquise (Milliardo Peacecraft). There, she becomes his second-in-command and the operator of the ZERO System, a powerful tactical computer, for the mobile doll forces. Her presence among the White Fang is tolerated by Zechs after she demonstrates a deep understanding of his own history and motivations.

Her key relationships are defined by conflict and opposition. Her most significant dynamic is with Relena Peacecraft, whom she simultaneously admires and seeks to challenge, believing Relena's ideals to be naive. She forms a working alliance with Zechs Merquise, acting as a dark observer to his plan to annihilate Earth's armies. She also develops a bitter personal rivalry with Quatre Raberba Winner, another Gundam pilot capable of using the ZERO System. Their clash culminates in a dramatic fencing duel inside the falling space fortress Libra, where Dorothy stabs Quatre and reveals the true pain behind her war-obsessed mask. She is also the distant cousin of Treize Khushrenada, another major power player who shares a similar, complex appreciation for the nature of war.

Over the course of the story, Dorothy undergoes a subtle but crucial development. She begins as a seemingly cold and manipulative antagonist, but her breakdown during the duel with Quatre reveals her vulnerability and the tragic flaw in her philosophy. Her plan to horrify the world into peace is ultimately rejected. In the aftermath of the conflict, as depicted in Endless Waltz, she reappears not as a warmonger, but as a catalyst for civilian action, using sharp rhetoric to goad the passive populace of Brussels into standing up against the Mariemaia Army, thus helping to secure a genuine, people-driven peace.

Dorothy possesses several notable abilities. She is a highly skilled orator and political strategist, capable of swaying entire councils with her words. She is also an exceptionally gifted fencer, able to hold her own against and even wound trained Gundam pilots like Heero Yuy and Quatre Raberba Winner. Most significantly, she is one of the rare individuals with the mental fortitude to master the ZERO System. Using it, she demonstrates phenomenal multi-tasking capabilities, strategically coordinating hundreds of mobile dolls in battle while simultaneously piloting a suit and engaging in conversation, all without losing her sanity to the system's overwhelming mental feedback.