Prior to the Cataclysm, Lord Soth was a Knight of the Rose, one of the highest of his order, who
forsook his position through the murder of his wife after seducing an elven cleric. When she
discovered what the gods planned for Krynn, she prayed to Paladine to grant Soth the power to
stop the Cataclysm. Lord Soth forsook his quest for because of jealous notions planted in his
head by elven clerics he met on his way to Istar. Upon returning to Dargaard Keep on the
Night of Doom, he entered the castle as the fiery mountain struck Krynn, killing his wife
and child--but not before she cursed him for his treachery. Lord Soth now roams
Krynn as a death knight; his men at arms are now his legion of undead. The elven clerics
reside there as well - banshees who sing each night to the fallen Knight of Solamnia,
telling of his fallen and never-ending punishment.

Reference: Knight of the Black Rose's cover