The Hero of Chasms of Malice was third-assistant-rabbit-skinner in the under-kitchens of Gorak Keep. Astragal, wizard of the Mage Order, used the Crystal of Bahriyya to identify the hero as a blood heir of Tancred the Magnificent.
Many years ago Tancred's line of descendants was thought to have ended and the stewards of the Ridermark took control of the kingdom until a suitable heir was found. When the Great Seals of the True Shield were somehow broken and the Malice was released once more, an heir was required as only a descendant of Tancred could wield the Shining Sword, one of the mighty Twin Swords of Light, which would "strike fear into the heart of Orghuz".
The heir entered the chasms below Gorak and finally laid the spirit of Orghuz to rest and destroyed his Khuddam followers, retrieving the True Shield to once more protect Gorak from the Malice. Upon his or her return, the Knights of the Grey Horse swore allegiance to the new sovereign of Gorak.
Given that the hero started as a kitchen servant and ended as a monarch, it seems unfeasible for him or her to have featured in any other books in the main series.