In the anime "Reign: The Conqueror," Alexander is reimagined as a futuristic and philosophical version of the historical Alexander the Great. He is the Prince of Macedonia, the son of King Philip II and Queen Olympias, a woman deeply involved with pagan rituals and prophecy. From his birth, he is burdened by a prophecy foretold by the mystic Pythagoras that he will one day destroy the world. This foretelling defines his existence and fuels the central conflict of his character: the struggle between his ambition for creation and his destiny as an agent of destruction.

Alexander's personality is marked by an aloof and introspective nature, often appearing detached from the political machinations and emotional turmoil surrounding him. Unlike the straightforward conqueror of historical accounts, this version is driven by a profound and abstract desire to attain speed, which he believes is the ultimate tactical advantage in battle. This pursuit of speed is more than a military strategy; it represents his philosophy of surpassing human limitations. He is portrayed as clever and unrivaled in his tactical thinking, yet his demeanor is often spacey and contemplative, leading some observers to interpret his behavior as being detached from reality. Alexander embodies passion and emotion in direct opposition to the stoic rationalism taught by his former tutor, the philosopher Aristotle.

His motivations evolve throughout the series, beginning with a need to prove himself and surpass his father's legacy. After ascending to the throne following Philip's assassination, which he and his mother are implied to have orchestrated, his quest becomes a messianic crusade to unite the known world. He is driven by the belief that he is a god, or destined to become one, and that his conquests will usher in a new era of understanding. This divine ambition is constantly shadowed by the prophecy of destruction, creating a duality where his actions are simultaneously creative and ruinous. He seeks to understand the mysteries of the universe, often seeking out philosophers like Diogenes, who challenges him to reconsider destruction as a form of creation.

Within the story, Alexander serves as the central axis around which the fates of empires and philosophies revolve. His role is that of a transformative, almost cosmic force who challenges the established order of the world, which is symbolized by the Platohedron, a geometric device containing all knowledge. His military campaigns against Athens, Persia, and India are not just political conquests but philosophical clashes between his world of dynamic passion and the old world of rigid logic. He is a visionary leader who inspires intense loyalty among his companions, such as Hephaestion, Ptolemy, and Cleitus, even as his relentless drive eastward tests their faith and leads to tragedy.

His key relationships are deeply complex and often fraught with tension. His mother, Olympias, is a source of both affection and psychological manipulation, as she gleefully nurtures his destructive destiny. In contrast, his father, Philip, views him with suspicion and fear, creating a deadly rivalry for power. His friendship with Hephaestion is portrayed as his most intimate bond, a source of emotional stability that is shattered by the latter's death. Aristotle, his teacher, acts as a philosophical antagonist, eventually plotting to have Alexander killed to prevent the world's destruction, highlighting the breakdown of their mentor-student relationship.

Alexander undergoes a significant, albeit internal, development. He begins as a young prince eager for glory and ends as a world-weary figure who confronts his own mortality and the consequences of his ambition. Initially, he resists the idea that he is a destroyer, seeking alternative interpretations of his fate. However, after a journey to the edge of the world and an encounter with Pythagoras, he accepts that destruction is necessary for rebirth. This acceptance does not lead to a nihilistic end but to a transcendent realization. In the final moments of the series, after returning from his campaigns, he watches a young child named Euclid drawing geometric figures in the sand and declares that he is witnessing the world he destroyed being made anew, suggesting his conquests cleared the way for a new age of knowledge and reason.

In terms of abilities, Alexander is a peerless warrior and military strategist. He is renowned for his cleverness and his signature tactic of exploiting speed to break enemy lines. He is the only one capable of taming the wild, man-eating horse Bucephalus, who becomes his loyal steed and a symbol of his raw, untamed will. While the world is filled with advanced technology and humongous mecha, Alexander relies on his personal combat skills, wielding a sword with deadly precision. He also displays a unique resistance to manipulation and a sharp intellect that allows him to cut through philosophical knots, such as when he physically severs the legendary Gordian Knot instead of attempting to untie it. His greatest ability, however, might be his sheer force of will, which allows him to influence events on a metaphysical level, ultimately leading to the collapse of the Platohedron and the reshaping of reality itself.