Ari hails from Thorfinn's Icelandic village, with jet-black hair often tied back and hazel eyes. His early attire featured a brown tunic with ash-gray sleeves, black belt, ash-gray pants, and brown shoes. After joining the military, he adopted chainmail, a helmet, and a distinctive red scarf, later growing facial hair by 1018.

As a youth, Ari burned with ambition and eagerness for combat. He carried unreturned affection for Ylva, oblivious to another village girl's feelings—a freckled companion who bid him farewell. Driven to prove his worth, he joined Thors' ill-fated war expedition, where his enthusiasm faltered on the battlefield. Following Thors' death, Ari furiously confronted Askeladd but was swiftly overpowered.

He harbored lasting resentment toward the man who disabled his brother by severing his left leg. Yet Ari remained capable of warmth, visibly delighted when Thorfinn returned to Iceland years later. He listened to Thorfinn's tales of distant travels with evident shock.

Ari eventually married Ylva, and they raised four children by 1018. He maintained strong village ties, appearing at significant events like Sigurd's homecoming and participating in gatherings, including weddings. Ultimately, he joined Thorfinn's westward voyage to Vinland among the settlers.