The Edge of Empire
The Otherworlder, aka P’lchrukk, is a being of unknown origin and fabled malevolence who once ruled the area now called The Fallen Lands, along with the Swamp of Chelimber, the nearby mountains, and most of the Greyflow River.
It ruled with the power of a demigod, worshiped by some. Foremost among those who gave it fealty were its three generals, whose internal warring eventually provided opportunity for P’lchrukk’s foes to get the upper hand and banish him to the Shadowfell, sealing the breach and imprisoning him forever.
The Keep on the Shadowfell is the fortress that guards the seal. The Spellplague has weakened the seal and caused P’chrukk’s corrupting influence to spread.