Gerlun was an initiate of the Malevolence, which was a cult comprised of Dark Jedi residing within Andeddu's Keep located on Prakith. In the year 137 ABY, Darth Wyyrlok III made an appearance at the Keep, his purpose being to uncover the hidden knowledge of Darth Andeddu and utilize it to support Darth Krayt, the Dark Lord of the Sith. Gerlun, along with the other Dark Jedi, engaged in a confrontation with the visiting Sith Lord. However, they proved to be unequal to Wyyrlok's proficiency with the Force, and Gerlun, while under the sway of a Force illusion, attacked and killed Demtri. Shortly thereafter, Darth Wyyrlok chose to let Gerlun live but proceeded to eliminate the remaining members of the group with Force lightning.
Wyyrlok compelled Gerlun to lead him to the burial chamber of Darth Andeddu. Upon entering, Darth Andeddu's holocron attempted to persuade Wyyrlok to position the holocron upon Andeddu's physical form, but Wyyrlok declined. Seeking to exact retribution upon Wyyrlok, Gerlun employed the Force to seize the holocron and place it on the corpse. This action, regrettably, resulted in his life force being drained, leading to the reanimation and subsequent destruction of Darth Andeddu.