Caveat: I am going to use many inappropriate terms herein, like species or maybe even gravity, both of which are concepts essentially outside of Gloranthan consciousness. These inappropriate vocabulary usages here should not imply that use of these concepts occurs within Glorantha.
Greg Sez is an ongoing column of material made available by Greg Stafford, creator of Glorantha. Other columns of Greg Sez include:
Q: What is so special about the Lunar Hell(s)? Why is there no escape for imprisoned souls (for example Sheng Seleris)?
A: Every deity has their own parts of the Underworld. They can be places of bliss, punishment, or nothingness. It is possible to Heroquest in your own Hells because your religion teaches you about it, how to deal with it, and how to get in and out of it. The Hell of any foreign deity is always tricky because the Orlanthi Land of the Dead (for instance) is different from the Yelmic Land of the Dead, even though they fulfil similar functions. Sheng Seleris was sent to an unusually difficult Hell, though, because the deity which he offended a mystical deity, not just a divine deity. Mysticism looks at the world is a different way than the gods altogether, and so getting to him requires an entirely different mind set and set of powers. Hence Argrath's need for a double death quest.
I shall quote the Unrealized Mushunasan, who first taught of mystical consciousness to humankind. He who is Not Great or Ungreat said, "The path of Unrealization is extremely hard and fraught with temptations, for successful meditatiors acquire great personal powers which they can wield if they break their life of Unrealization. When weak people set upon the path and fail they have petty powers, and by exercising them they turn into monsters. Powerful men who fail become as demigods, like Sheng Seleris, and turn into demons. Great beings who fail become as gods, and turn into antigods, like Oorsu Sara. Since all demons, monsters, and antigods are hunted and destroyed by all true beings, whether humans, demigod, or god, all nonunrealized beings live troubled and unhappy lives. Furthermore, whatever success they achieve will eventually be opposed by a greater power, for such is the cosmic law of the world. But as dire as those lives are, death is worse for those who have renounced Unrealization. Their former detatchment fills with matter which drags their souls into a hell as deep and horrible as their greatness had been. There they stay until they are purified, and able to reenter existance in a balanced manner."