The Nine Hells
Tartarus exists as the warped remnants of an ancient celestial prison, ruled by its former long time prisoner, 🔥Prometheus. While many other prisoners of old had long since vanished, forgotten to time, Prometheus existed out of pure spite and a longing to seek retribution on those he felt had wronged him.
If a soul is sufficiently evil, regardless of its proclivity for worship or its devotion to a God, it may still end up in Tartarus by some sort of cosmic law placed into effect long ago, perhaps even before the war between the 🪐Archons and the 🪼Grotesques.