A wolf is a large canine. Wolves usually serve Lupa, the leader of Camp Jupiter. Wolves are social predators that generally live in families or packs, although they do sometimes live alone for various reasons. In areas where human cultures and wolves both occur, wolves are frequently featured in the folklore and mythology of those cultures, both positively and negatively.
In Norse mythology, wolves are revered as the sacred animals of Odin, along with ravens. Fenris Wolf is a prominent character in Norse myth, as he is the son of Loki and takes the form of a large blue wolf. He was captured and imprisoned by the gods due to his destiny being to eat the gods during Ragnarok, the end of the world.
The Heroes of Olympus
The Lost Hero
Jason Grace has a dream where he stands in Redwood Forest, and a pack of wolves circle around him while the ruins of a stone mansion arise. The wolves eventually lead him to Lupa, who gives him hints to his past and makes a joke that hinted about his identity as being Jason Grace.
Later on, a group of lycanthropes attack Jason, Leo Valdez, Piper McLean, and Gleeson Hedge. They are led by Lycaon, the first werewolf, and according to him, they are the enemies of Lupa and her pack. Lycaon also harbors a grudge against Zeus and his children for turning him to what he is. The Hunters of Artemis scare them off or kill them with their silver arrows, silver being the only metal that can kill them.
The remaining lycanthropes appear at the Wolf House and fight with other monsters against the demigods. They are killed or scared off when Hera transforms into her Divine Form.
It is also shown that the Hunters of Artemis have their own pack of wolves that they use for hunting and tracking. It also appears they have some level of communication with them, most likely from being a hunter.
The Blood of Olympus
Reyna Ramírez-Arellano, Nico di Angelo, and Coach Hedge have a run in with Lycroan and his wolves in Évora, Portugal.
Magnus Chase and the Gods of Asgard
The Sword of Summer
Two magical blue wolves sent by Fenris attacked Magnus Chase and his mother in their Boston apartment. Magnus survived, but his mother was killed by the wolves. This leads to Magnus having a vendetta against the animals.
Wolves appear throughout the Hotel Valhalla as they are sacred to Odin, much to Magnus' chagrin.
The Island of Lyngvi contains Fenris Wolf, a monstrous wolf destined to eat the gods alive. As his bonds are beginning to fail, Magnus and his friends Samirah, Blitzen and Hearthstone travel to his island during the solstice in order to replace his rope with a new, better one. However, Fenris Wolf almost manages to escape.
The Hammer of Thor
Otis is assassinated by a mysterious killer wearing a wolf mask.
The Trials of Apollo
The Tyrant's Tomb
Lupa and her wolves arrive during the funeral of Jason Grace and the she wolf speaks with Apollo.