Greel's ancestor is, as the name suggests, the ancestor of Greel, and thus the ancestor of Glock and Gers. He was the Jalis that accidentally killed one of the seven goblins in the Tenna Birdsong TaleThe Seven Goblins. The dead goblin was a member of the Plume tribe carrying the mouthpiece of the Pirran Pipe. At the time Greel's ancestor did not realise all this and thought the mouthpiece was merely a goblin talisman for protection.
Tales of Deltora
One day a man of the Jalis tribe and the ancestor of Greel, came home to his hut after a long day. He threw himself upon his bed, crushing the wooden bed and a Plume that lay underneath it. Later when he removed the broken wood he found the body of the dead Plume, mistaking it for a goblin. He noticed the pouch that hung around its neck. The Jalis claimed the pouch and the tiny object inside it, a wooden mouthpiece of a flute, and wore it around his neck as a protective talisman.
Adin encountered Greel when he travelled through diamond territory to collect the seven gems. Greel fought Adin and emerged victorious but instead of killing Adin, Greel allowed him to feast with the Jalis that evening. The next day Greel would kill him. Greel also spoke about his clan. He mentioned his ancestor and the fact that he had killed a goblin in the hut in which Greel now lived. Greel also showed Adin the talisman that once belonged to the goblin and had been passed down to him over the generations.
Cavern of The Fear
The Jalis would go on to pass it down to his descendant, who passed it on to his descendant, ending with Glock, one of the last survivng members of the Jalis tribe who lived in the time of King Lief. When Glock died in the Pirran Caverns near The Glimmer, the talisman was passed on to his friend Jasmine. In that moment it was revealed to be the mouthpiece of the fabled Pirran Pipe.
In the Shadowlands the companions encountered the Resistance including the Jalis Gers. It turned out that Gers is the brother of Glock as he recognised the talisman and the aphorism when confronted with it by Jasmine.
Not much is known about the physical appearance of Greel's ancestor. As a Jalis he shared much of the Jalis animalistic traits.
Greel's ancestor rejoiced in fighting and went on raids that lasted months. Lying did not matter to him if this meant he could boast about his deeds. He was also superstitious because he thought that the goblin talisman would offer him protection.
Greel's ancestor was a savage fighter. He also had some leadership qualities as he was the head of his clan.
Greel's ancestor thought the talisman would offer him protection. Ironically the mouthpiece could really only offer protection, specifically against the Shadow Lord, when it was restored to the full Pirran Pipe.