Lupa

Lupa is the immortal wolf who trains demigods in the ways of Rome. She trains Roman demigods at the Wolf House then send them to Camp Jupiter where they can join the legion.

Caretaker of Remus and Romulus
Remus and Romulus were the twin sons of Mars and Rhea Silvia who were thrown into the River Tiber at the command of their great-uncle Amulius. They were saved by a great she-wolf who nurtured and raised them as her own young. Having grown strong under her guidance, the twins would go on to destroy Amulius and establish the city of Rome.

The Lost Hero
Lupa contacted Jason 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. It isn't until he learns who he is that he understands what Lupa meant. 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.

The Son of Neptune
Lupa was mentioned by Percy in The Son of Neptune. According to Percy, she promised him that he would see Annabeth again if he succeeded in his quest. She apparently taught Percy to sharpen his senses, the "homing senses" that had led him south. She also told Percy his name after Hera took his memory. It is also said that her pack slowed down the army of Polybotes on their way to Camp Jupiter. However, she did not interfere with the final battle at the camp as it is not her way.

Appearance
She is described in wolf form with beautiful chocolate red fur and eyes as silver as mist. She is also described as being very tall, taller than any human. In Jason's dream, she was seven feet tall.

Trivia

 * Interestingly, as leader of the Roman Camp, she still knew where Jason Grace was and was able to contact him in a dream. And yet Chiron, the director of the Greek camp, has not made any mention of being able to contact Percy, though possibly because it was Juno, Hera's Roman counterpart, that switched the two leaders, its likely that she informed Lupa beforehand as to not harm Percy for being a Greek demigod.
 * Her name Lupa, probably is the female form of the Latin word for wolf (lupus), which would make her name mean literally She-wolf.
 * Her name could also originate from the word luna which means moon.