Hallows Gate is a specific Ether Pocket, and more consequentially, a Gate Plane. Not created by Elder Dragons or Primordials, its origins are a mystery. In known history, Nyrghaul discovered the Gate, while following the fleeting soul of Dathix, when the latter was slain in the last battle of the Dragons' rebellion. Nyrghaul was able to master the Plane, releasing Dathix's soul into the Void.
The Death Aspect, a highly focused ward of bound ether, was crafted by Nyrghaul to control the Gate. He would use it to continue to send the souls of the Draconic Races beyond the Gate. After his demise at the end of the Primordial Wars, Varthiir controlled the aspect, but failed to utilize it, causing the souls to bottleneck at the Gate and eventually become Revenants.
Eli would eventually gain the Aspect from Varthiir, before passing it to Kalas after the Banishment of the Dark Source through the Gate. Kalas currently resides and holds mastery of Hallows Gate, sending souls beyond to avert another Revenant Crisis.
The Plane's form can be manipulated by the Death Aspect, but whether the owner wishes it or not, the Plane allows residence only to the dead (or beings protected by immense power). All others are stricken dead should they enter. The Timekeepers have mused that the Hallows Gate is perhaps a defence against the Void, designed to slay what enters, and its use as a exit conduit for souls purely circumstance.
Primordials and Primordial Races alike are not drawn to the Hallows Gate on death, the process of their death is somewhat unclear, with most of the latter's beliefs emphasizing reincarnation and rebirth.
Most Dragons also simply dissipate back into elemental ether when slain. The Elder Dragons seem to be an anomaly with Dathix being sent through the Gate, Nyrghaul being absorbed by his killers, Alestraxia's essence remaining in various forms, and Aquar's unknown fate. Thul'Masira seems to have also left her essence in concentrated form in Shadowsfall Lake.
Hallows Gate has a breach point with the physical world of Akrylonor at Hallowswatch, an Underworld settlement of the Ghaulsyr, that tend this potential portal carefully, at the behest of Nyrghaul's dying wishes.