Sumarbrander

''This article is about the sword. You may be looking for the book.''

Sumarbrander, also known as the Sword of Summer, or Jack, is Magnus Chase's sword and companion, formerly owned by his father, Frey. He is said to be the sharpest sword in the Nine Worlds. At the sword's request, Magnus renames him Jack after becoming its master.

History
Sumarbrander is a magical sword, originally owned by the Vanir god Frey. Frey fell in love with a frost giant, Gerd, who he was not allowed to marry. Frey ended up trading his sword to Skírnir, his servant, to kidnap Gerd and bring her to him. It sunk on a Norse ship in Boston, where he was found and renewed by Magnus Chase. Sumarbrander ended up being betrayed by its original master, although he continued to obey Skirnir. Sumarbrander (Jack) is one of the most famous swords in Norse Mythology.

The Sword of Summer
Magnus retrieves the sword from the bottom of the sea before Surt attacks him. Magnus comments that it didn't really look like a sword - it looked more like a lead pipe and was corroded, crusted with barnacles, and covered in mud and slime. He renews it during the fight with Surt. After he dispels Surt with the sword, he loses it at the bottom of the ocean after dying in the human world. After retrieving the sword by bargaining with the sea goddess, the sword turns into a pendant with the rune of Frey on a chain.

When visiting Freya, Magnus learns about Sumarbrander's past with its original owner, Frey. Freya tells Magnus that the sword has "special abilities" that he will need to learn to master.

While running away from Junior, Magnus pulls out Sumarbrander, who ends up having the ability to talk. After disarming all the attacking svartalves, Sumarbrander is given the name Jack. Before they flee Nidavellir Jack tells Magnus that if he touches him too soon the demigod could pass out or die.

He was then used to track down Thor. When Magnus and Sam get Gerriod's daughters to admit they tried to kill them he scrambles their brains.

When they reach Lyngvi, he desperately tried to get to Surt. After Magnus snaps him out of it, he ties the new rope to Jack to tie up the wolf. Magnus then uses Jack to heal Halfborn Gunderson.

When he and Magnus greet Frey, he desperately tries to attack the lord of Alfheim.

The Hammer of Thor
Magnus call on Jack when Otis was killed by an assassin. He went on to attack their target while Magnus was hoisting himself onto a roof. He fought with the assasin and managed to cut into the assasin's thigh. Jack was disapointed that he could not cut through the assasin's sword. But Magnus managed to chear him up.

When Magnus returns to his room he asks Jack to ask him about a mark that appeared on a picture and pottery. Jack tells Magnus that Mjolnir can be taken if someone has the numbers and the strength to do so. T.J. pops in to tell Magnus it is time for battle practice. Magnus was surprised to learn that the two of them hung out the night before, he skipped out on battle practice due to a date with a polearm.

Appearance
In its dormant form, it's a small white runestone emblazoned with a black symbol: the Fehu rune- the symbol of Frey on a golden chain. The stone is magnetically attached to its chain, so it can easily be pulled off, and as soon as it is, the stone grows into a sword with a leather-wrapped grip that feels warm and comfortable to the hand. The pommel, a simple polished steel oval, helps counterweigh the thirty-inch blade, which is double-edged and rounded at the tip, more for hacking than stabbing. Down the center of the blade, a wide groove is emblazoned with Viking runes that shimmer in a lighter shade of silver, as if they'd been inlaid while the blade was forged.

Abilities
Jack is a sentient blade; it has the ability to speak and understand human language (although, as it says, it can't speak Alf Sign Language, most likely because it has neither hands nor eyes).

Jack is also very effective against the Jotun, and it can fight them on its own. It is also the only thing capable of cutting through Gleipnir. Whenever the holder of the blade retrieves it after an action, they receive the consequences of the action that the sword has performed.

Etymology
The sword's Old Norse name means "Summer Sword".

Trivia

 * In the mythology, Frey's sword is never named.
 * When wanting to be named, it mentions that it never liked the name Sumarbrander because it was so long.
 * After Sumarbrander begins to speak in The Sword of Summer, its voice is described "definitely male"and is then on described using male pronouns.
 * Sumarbrander is destined to become Surt's possession and kill Frey during Ragnarök.
 * When discussing what form should Jack become when not a sword, Magnus suggests a pen. Jack comments that a pen sword is 'the stupidest thing he's ever heard'.
 * This is a nod at Percy Jackson's sword, Riptide, which becomes a pen when "capped".