Loki

Loki is a trickster half-Jotunn Norse god, and an enemy of Magnus Chase. While treated as a nominal member of the Aesir tribe, he is known to switch his allegiance often and is destined to ultimately side with the giants and lead them against the gods. He is the father of Hel, Lady of the Dead, Jormungand, the World Serpent, Fenris, the Wolf, and Samirah al-Abbas.

The Sword of Summer
Loki frequently appears in Magnus Chase's dreams to convince him to give up tying the Fenris Wolf. The first time was when Magnus died. The second was after Magnus' first battle practice where he told Magnus he would eventually sit on Odin's throne. The third was when Magnus and friends jumped into a river to get out of Nidavellir and promised he would be reunited with his mother in Helheim if he gave the sword of summer to Randolph. Loki hopes to bring Ragnarök by manipulating Randolph Chase. After Magnus re-tied his son, Loki appears in Randolph's office, revealing he was the priest at Magnus' funeral. He gives Randolph a burn scar on his face for failing him. He says that their are many triggers for ragnarök.

Personality
Loki is sly, manipulative, charming, humorous, mischievous, quick to anger, and cruel when he needs to be (demonstrated when he burned Randolph Chase's face as punishment for failing him). Rick Riordan says he wrote Loki as he was in the myths: "[...] clever, funny, capricious, silver-tongued and quick to anger,". Loki is also extremely persuasive, to the point that he once successfully convinced Ran to lend him her magic net.

Despite his negative traits, Loki does harbor affection for his children, especially Samirah al-Abbas, Vali, and Narfi. When speaking to Magnus on Naglfar, Loki is visibly upset and grieved about the shocking fate that his sons Vali and Narfi suffered as part of Loki's punishment for killing Balder - with them being slain by the gods, and their entrails used instead of ropes to bind Loki to a the slab of rock under a serpent.

Appearance
In The Sword of Summer, Loki has dirty blonde feathery hair (with red, blonde, and yellow tints), tousled in a fashionable I-just-got-out-of-bed-and-I-look-this-good sort of way, and he is seen wearing a Red Sox jersey, jeans, and white tennis shoes. Loki is considered shockingly handsome, though his appearance is somewhat ruined by his scars - burn tissue splashed across the bridge of his nose and his cheekbones (caused by the snake venom dripping onto his face), like impact lines on the moon's surface, while Loki's lips are marred by a row of welts all the way around his mouth, much like many piercing holes that had closed over (marks from the time his lips used to be sewn together by the dwarves).

Loki's eyes have an intense glow to them, much like those of his daughter Samirah, with his gaze flitting restlessly, like fire in a hearth, pushed by the wind, looking for anything it could set ablaze.

Abilities

 * Illusions: Loki can cast illusions of himself anywhere he pleases. He can still enter demigods' dreams, even as his actual body remains securely imprisoned (until Ragnarök).
 * Shapeshifting: Loki is able to change into various forms including, but not limited to, a salmon, a mare (in this form he even gave birth to the colt Sleipnir), a seal, a fly, and an elderly woman called Thokk.
 * Enhanced Strength: When Loki grabs Magnus' wrist, the latter claims that his grip was "like steel."
 * Serpent Venom Pain Transferal: While touching Randolph Chase's face in The Sword of Summer, Loki was able to make the latter feel the extreme pain that the serpent venom causes when it drips onto the trapped god's face from time to time.
 * Consciousness Splintering: Despite being securely imprisoned by the gods, Loki can still make part of his consciousness materialize into another physical body from time to time, like when he visits Randolph in the epilogue of The Sword of Summer. If done incorrectly, however, this process can cause him intense pain.
 * Pyrokinesis (limited): Loki can create fire, shown when he created still houses of Randolph's wife and daughters made out of fire in his hand in The Sword of Summer epilogue.

Trivia

 * A joke was made in The Sword of Summer about Loki's name being similar to the English phrase "low-key."
 * During Ragnarök, Loki is destined to kill Heimdall, but is also destined to be killed by the latter.
 * Loki is associated with the Kenaz (or Kaunaz) Rune.
 * He was the one who tricked dwarves into making Odin's spear, Gungnir, and Thor's hammer, Mjolnir.
 * According to Utgard-Loki, the name Loki is a common one among the Jotnar.
 * In some versions, Loki was represented as the god of fire.