Leila

Leila is a legionnaire and an old comrade of Jason Grace. Her rank and cohort at Camp Jupiter are unknown, as is her immortal ancestry. She fought in the Second Demigod Civil War, led by Octavian, centurion of the First Cohort, and reluctantly by Praetor Reyna Avila Ramírez-Arellano.

History
Little is known about Leila's past. It can be inferred that she was trained at the Wolf House by the wolf goddess Lupa. At some point, she made her way south toward Camp Jupiter and was accepted into the legion by the augur.

It is unknown how long Leila has been a member of Camp Jupitr or even if she took part in the Titan War. However when Jason Grace sees her in a vision, he refers to her as an old comrade. It is also unknown if she fought in the Attack on Camp Jupiter, alongside Reyna Avila Ramírez-Arellano and the new recruit Percy Jackson, as she is never mentioned by name.

The House of Hades
After confronting the pirate Sciron, Jason fell into unconscious mid-air, dreaming about the Romans' gathering in New York before their planned attack on Camp Half-Blood. Jason recognized Leila among his old comrades, which also included Dakota, Nathan, and Marcus.

Leila was present when Rachel 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 Leila and the others that there were going to be some changes in the legion's plans.

Trivia

 * Leila is a variant of the Arabic name Layla, meaning "night."