When Dorian discovered the cavern had the property of allowing him to regenerate himself by transferring the negative effects of 'time and appetite' to another, he imprisoned his former partner there. Dorian was occasionally compelled to return to the cavern to carry out the transfer.
After two centuries Dorian found the process was beginning to fail and planned to replace the creature with a gestalt entity composed of Avon, his followers, and Dorian's lover Soolin. However Avon was able to shoot the creature. The accumulated ravages returned to Dorian who rapidly decayed and died as a result.
By this time the creature was barely humanoid and did not appear to be sentient. It bore a striking resemblance to a Phibian.