Absolutions were a class of "fatal channels" in the I.C.E. Age mechanics or Rolemaster system. They were instant death effects analogous to Sacrifice, where the soul was torn from the body. Spells of Absolution Pure were irrevocable in the absence of a high-level resurrection spell, and Dark Absolution would destroy the soul itself, forever ending the existence of the target. Very old spell lists refer to the soul as "needing to exist" for this reason. In the Shadow World setting, Dark Absolutions were always the work of servants of the Unlife, and were considered the worst possible fate in the religion of Eissa (Lorminstra). However, she would herself destroy hopelessly dark souls, using her Staff of Doom. The paradox is that our souls dissolved into nothingness in Purgatory regardless.
Possible forms of Dark Absolution included being "ordained", falling prey to malevolent artifacts, being fed upon by dark powers, as well as black curses, such as "Kadaena's Kiss" which melted away all of the flesh and kept the skeleton alive for hours in agony before the soul was destroyed. There was another such curse on the same spell list that liquified the skeleton, so the two in conjunction may explain the throne room in The Graveyard. In the "The Legend of the Necropolis of Etrevion" Bandur supposedly slayed Kestrel with a "Spell of Absolution Pure" in a fit of possession and rage.
Behind the Scenes
Pale Embrace was arguably a modern spell of this kind, which was used for assassinations in Elven courts. The rumored Master of Lore geas curse may have been similar. The Vaalor will execute the most severe criminals with a poison that prevents even Lorminstra from returning the soul to the body, though this is rare, and may be ignoring her power to reincarnate the dead from pure spirit. What truly distinguishes Lorminstra in GemStone is her reincarnation powers. The Sign of Hopelessness is an absolution effect as well, referring to the "hopelessness" messaging in Purgatory. The soul is ripped apart by the forces of darkness, but the tattered pieces are gently reassembled by the death goddess. She returns your soul to the world with your memories suddenly rushing back to you.