Abiriga is a central figure in Altair: A Record of Battles, initially appearing as a slave from the impoverished nation of Salos before rising to become a trusted aide and confidant to the protagonist, Tughril Mahmut. His background is marked by hardship; born into a country plagued by economic crises, he was sold into slavery by his own parents at the age of twelve or thirteen. Demonstrating fierce determination even as a youth, he escaped from a slave trader by jumping into the sea and swimming to a Venetian ship. There, he was rescued by Captain Silvestro Brega, but his first act was to snatch a blade and slash Brega across the face. Rather than punish the boy, Brega was impressed by his fighting spirit and purchased his freedom for five times his market price, effectively becoming his adoptive father.

In terms of personality, Abiriga presents a complex and layered character. On the surface, he is affable, friendly, and possesses a gentlemanly demeanor, often wearing a pleasant expression. However, this harmless exterior belies a crafty and cunning intelligence, a trait befitting a citizen of the mercantile city-state of Venedik. He is known to enjoy the thrill of battle, a characteristic that has earned him the descriptor of a blood knight; he relishes a good fight, though his near-superhuman physical abilities mean such opportunities are rare. Despite his mischievous and sometimes mysterious nature, which can make others like Cyrus wary of him, Abiriga is fiercely loyal to those he holds dear. He is willing to sacrifice anything for the happiness and well-being of his closest people, and he serves his masters—first the Bregas and then Mahmut—with unwavering devotion.

Abiriga's role in the story evolves from a spy and merchant for Venedik to Mahmut's private army commander and personal aide. He is first introduced when he and Captain Brega rescue a fleeing Mahmut and his companion, Cyrus. His transfer to Mahmut's service is a calculated test; Brega and the rival Coronna company orchestrate a scheme that forces Abiriga into exile over a debt, creating an opportunity for Mahmut to prove his worth by using his wits to earn the money to pay it off. Impressed by Mahmut's actions, Abiriga is effectively sold to him to serve as a liaison and strategic asset. From that point on, he acts as a vital pillar of support for Mahmut, using his knowledge of Venedik's political and commercial systems to aid in diplomatic missions and military campaigns. He is quick-witted and resourceful, often providing the pragmatic counterpoint to Mahmut's idealism.

His key relationships define his trajectory. Silvestro Brega is his savior and paternal figure, having recognized his potential and provided him with training in martial and warfare arts. This training molded Abiriga into an exceptionally formidable fighter. His relationship with Mahmut is one of mutual respect and trust; Mahmut sees him as an equal, while Abiriga sees himself as Mahmut's "battle butler". He is protective of Mahmut and consistently offers insight and levity in tense situations. His relationship with Cyrus is more complicated, as Cyrus is often uneasy around Abiriga, unable to fully penetrate the mysterious and elusive aspects of his character.

Abiriga undergoes significant development from a desperate, angry slave to a refined and capable agent of state. While his core attributes of loyalty and combat prowess remain constant, his character is revealed to have great depth. He demonstrates a capacity for genuine care and sacrifice, and his service to Mahmut gives him a cause larger than the mercantile interests of Venedik. His skills are vast; he is proficient in a wide variety of weapons, possesses "insane physical capabilities," and maintains a perpetual cool-headed state of mind even in the heat of combat, making him a terrifying opponent. Beyond combat, his talents include deduction, as shown when he identifies a valuable fertilizer source from a foul smell, and an intimate understanding of espionage and trade, making him an indispensable aide in both peace and war.