Oathsworn

"Memories of loss and dreams of vengeance, sealed in steel and composites. Mythic Shotgun with increased damage, accuracy, and rate of fire. The user's movement speed is also increased while Oathsworn is equipped."

- In-game description

Oathsworn is the name bestowed upon numerous custom-crafted shotguns. At least one of these shotguns was a modified M45D shotgun and was used by Kelly-087 in late 2558.

Background
The Oathsworn is an example of personalized equipment utilized by the Spartan-IIs, specifically Kelly-087. Many Oathsworn shotguns have existed over the years, with each being created prior to another mission after the previous Oathsworn had been lost or abandoned by Kelly on the battlefield. While each version of the weapon has its slight differences, the markings have remained the same for years. The words Kelly whispers as she rebuilds and tunes each shotgun change every time, but the intent behind them remains the same.

October 2558 Oathsworn
The Oathsworn used by Kelly-087 in October 2558 was a modified M45D shotgun.

Halo 5: Guardians
The Oathsworn is a mythic weapon in Halo 5: Guardians available as an Ultra Rare Level 5 REQ that grants 150 REQ Points when sold. As a slightly upgraded version of the Lawgiver, the Oathsworn has increased damage, accuracy, and rate of fire compared to the normal shotgun, features slightly more range and accuracy over the Lawgiver, and increases the user's movement speed while the weapon is equipped. As the weapon has a built-in Speed Boost, users of Oathsworn receive white auras and highlights, making them more easily visible on the battlefield.

In the campaign, the Oathsworn can be equipped only if Kelly is selected by a player in cooperative play. Because of this, the Oathsworn is the only special weapon in the game that cannot be used by the player in the solo campaign. The campaign rendition of the Oathsworn has the Speed Boost removed and is exactly identical performance-wise to a standard Shotgun, including the strong vertical recoil.

Trivia

 * The rabbit painted on the side of the shotgun is a reference to the nickname Kelly-087 that earned for her impressive speeds, "the Rabbit."
 * Near the trigger, the words "REMEMBER REACH" are etched onto the weapon, referencing humanity's disastrous defeat at the key Inner Colony of Reach in 2552.

List of appearances

 * Halo: The Fall of Reach - The Animated Series
 * Halo 5: Guardians
 * Halo: Official Spartan Field Manual
 * Halo: Lone Wolf
 * Halo: Shadows of Reach