Lorekeeper: Erys
A small port city between the Material Plane and the Hells themselves.
Long ago, an ambitious fiend lord hatched a plan to pull an entire world out of the material plane and into the Hells themselves. Their scheme was foiled at the last moment by a motley band of heroes, leaving the planet formerly known as Edonia 99.9% in the Hells, with only a tiny landmass still in the Material Plane... and a border that you could walk across.
A major component of the heroic intervention that stopped the occlusion of the world of Edonia into the Hells was the creation of a magic barrier that prevented fiends from travelling to the realspace portion of the world without the usual summoning magic, however natives of the Material Plane could easily cross back and forth between the two. This created an enormous opportunity for both mortal and fiend, and a bustling trading port quickly grew up on what was left of Edonia and became known as Hellspike.
Many in the material world see an open doorway to the fiendish planes as a threat to at best the moral order, and at worst the very physical integrity, of the Material Plane. A great many fiends and their diabolic cults wish to see the barriers preserving Hellspike ripped asunder so that the dark forces they hold back can flood into realspace. Both of these movements are held in check by the incredible wealth and opportunity generated by trade between the two realms. Enterprising fiends offer the vast resources of the Hells, such as wealth, raw materials, and fiendish mercenaries, to sale for mortals who bring souls, services, and rare magic artifacts and materials to the port.
While Hellspike may have the appearance of a lawless town of excess and debauchery, underneath this veneer is a firm rule of order. Both mortal and fiendish guards working in service of Hellspike's richest merchant patrons prevent any activity that might threaten the stability of the world and the profitability of its commerce from becoming a problem with ruthless efficiency.
Think Firefly lands in Dante's "Inferno". Hellspike has a very Wild West feel, if the saloons were full of devils and the 3:10 to Yuma was hauling a cargo of tortured souls. You can buy or sell almost anything in Hellspike, and there are always those with jobs that need doing on either side of the barrier looking for adventurers willing to risk everything for a quick profit.