From Destinypedia, the Destiny wiki
The Haul is a massive, roughly spherical object towed behind the Drifter's ship, the Derelict. It contains a pocket of Unknown Space as part of the Nine Realms much similar to the Third Spire., accessible via an opening in the side facing the Derelict. The location within this pocket serves as the playing field for the Reckoning, a challenge co-orchestrated by the Emissary and the Nine.
According to an analysis conducted by the Praxic Warlock Aunor Mahal, the Haul is an "engine of pure potential," seemingly capable of manifesting any entity imaginable by its user. The Drifter has taken advantage of this ability by hooking up his banks to the Haul, allowing him to create "counterfeit" Taken Primevals for his games of Gambit Prime.
The Haul was gifted to the Drifter by the Nine, appearing seemingly out of nowhere after the Drifter was visited by the Emissary. However, the Drifter himself has claimed that he found the Haul in a place "cold enough to snuff out your Light," seemingly alluding to his misadventures on an icy world where he encountered Light-suppressing creatures. It is unknown if the Drifter is simply lying about his acquisition of the Haul, or if he encountered it prior to returning from his travels outside the Sol System.
- It is unknown whether or not the wiring from the Haul is Egregore as it does share some similarities in appearance to it.