Lupa is the immortal Roman wolf goddess who trains Roman demigods in the ways of Rome. She trains the demigods at the Wolf House, then sends them to Camp Jupiter where they can join the Twelfth Legion Fulminata.

Lupa contacts Jason Grace in his dreams to warn him about Gaea inadvertently. She also calls Jason their "Saving Grace," and curls her lips in a smile as if she just made a joke. Jason, not knowing his last name at the time doesn't see the humor but later realizes it. It isn't until he learns who he is that he understands what Lupa had meant by it. Later, when Lycaon attacks Jason and his friends, he makes a reference to Lupa, saying that soon Lupa would have to think twice before attacking his pack.