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Koraboros is a pit fiend who was trapped within Ammon Jerro's haven in the Sword Mountains, for the purpose of empowering the warlock. He was in a constant feud with several of the other imprisoned demons and devils, but broke free when Baalbisan convinced Shandra Jerro to spill her blood to undo the magic that bound the demons to the haven.

Once he returned to Baator, Koraboros began to plot revenge upon Jerro for imprisoning him. Eventually he was able to lure Jerro to the ruined farm his granddaughter Shandra had once owned. Koraboros appeared before Jerro and attacked him, but Jerro was able to overcome the pit fiend with the assistance of his new found ally, the Kalach-Cha. The Kalach-Cha later journeyed to the academy of shapers and binders in Thay, where 2 pit fiends, Oronock and Thael'ka, informed him/her that Koraboros had suffered a painful 'demotion ceremony' for his failure to defeat Jerro.