Nathan is a legionnaire and an old comrade of Jason Grace. His rank and cohort at Camp Jupiter are unknown, as is his immortal ancestry. He fought in the Second Demigod Civil War, led by Octavian, centurion of the First Cohort, and reluctantly by Praetor Reyna Avila Ramírez-Arellano.
Little is known about Nathan's past. It can be inferred that he was trained at the Wolf House by the Wolf goddess Lupa. At some point, he made his way south toward Camp Jupiter and was accepted into the legion by the augur. It is unknown if he fought in the Titan War or defended Camp Jupiter against the attack against it, but Jason Grace knows him and considers him an old comrade.
After confronting the pirate Sciron, Jason fell into unconscious mid-air, dreaming about the Romans gathering in New York City before their planned attack on Camp Half-Blood. Jason recognized Nathan among his old comrades, which also included Dakota, Marcus, and Leila.
Nathan was present when Rachel Elizabeth Dare arrived with Grover Underwood, as ambassadors from Camp Half-Blood. Rachel provided Reyna with a message from Annabeth Chase. Upon this, Reyna departed for Greece, reluctantly leaving Octavian in charge. As soon as Reyna was out of earshot, Octavian told Nathan and the others that there were going to be some changes in the legion's plans.
- Nathan shares his name with Nathan Fillion, the actor who portrays Hermes in Percy Jackson: Sea of Monsters.
- However, Rick Riordan has not seen the film series, meaning that the two sharing the same name could be a coincidence.