Antharia Jack is in-universe the canon hero from the original trilogy
After the hero became The Dungeon Master, and not only became elderly but also took on the intelligence and wisdom, he eventually turned back into his normal self after Dalboz succeeded him. (Losing said wisdom and knowledge) Though as a side affect from losing his Dungeon Master powers, his aging permanently stopped. He created and starred in television shows that he based on his adventures (Which consist of killing a troll with a rusty knife and a thief that "stole all his stuff") though he pretends that it's all made up, to keep the truth hidden. He even said that he had experiences with electric lanterns. (Enough to become a lantern repairman). Grues are monotremes
Frotzing grues in the Enchanter trilogy shows that they have fur, and grue milk is required for the Darkness spell in Wishbringer. However, grue eggs are shown in Zork: Grand Inquisitor. In other words, they're egg-laying mammals.