Mirthal was a wild elf (green elf) of the Suldusk tribe of the eastern Forest of Tethir, known as Durmista. He was very short for an elf, standing only five feet tall. He also had a quiet, melodic voice, which seemingly conflicted with his great skill as a powerful warrior.
Mirthal had a great talent for diplomacy, often able to avoid conflict more quickly with his words than with his dagger or wizard spells. His views were less extreme than those of Count Sylvanus Moondrop, which was in part why he was chosen for his position as one of three representatives of the elves of Tethyr.
Mirthal was a member of Clan Aendryr, one of the three remaining Suldusk families. His cousin was Tarasynora Aendryr, who had been tasked with teaching the elven children of Durmista magic. The clan was small and not considered a great tribe among the other Sy'Tel'Quessir.
Mirthal was married for 40 years, and he and his wife had twin daughters in 1363 DR. Sadly, his wife died in 1364 DR during the battle at Zoastria's Stand. Since then, Mirthal made it clear that he had no intentions of re-marrying, but this did not stop the human and half-elven women of his court from thinking he needed help raising his two daughters.
Mirthal retained strong friendships with each of the members of the former Company of Eight after his departure.
After his retirement from the Company of Eight, Mirthal maintained one of their safehouses in the southeast of the Forest of Tethir, known as The Eight's Tree. When he needed to hold court as duke, he did so at The Eight's Tree.
As duke of Durmista, Lord Aendryr was also a member of the Queen's Royal Privy Council. As Scoutlord, he was responsible for the training and direction of elite units of human, elven, and halfling scouts for the kingdom of Tethyr. In this role, Scoutlord Aendryr served directly under Vajra Valmeyjar. He was responsible for the creation of a secret unit of saboteurs.
Mirthal forbade any logging within the forest, which caused conflict between the elves and the human villages nearby.
Mirthal joined the original Company of Eight in 1344 DR as one of its original eight members. Around 1357 DR, however, he decided to go back to his home and left the Company. He was replaced by Manfred Arbustle.
- There is a conflict between sources regarding Mirthal's elven subrace. Hall of Heroes calls him a Suldusk wood elf, but Lands of Intrigue and Lost Empires of Faerûn describe him as a Suldusk green elf and Sy'Tel'Quessir. Since Lands of Intrigue clarifies his subrace with the elven name, and since the Suldusk tribe is elsewhere described as containing wild elves, the later sources are trusted in this case.
- Steven E. Schend (1997). Lands of Intrigue: Book One: Tethyr. (TSR, Inc.), p. 66. ISBN 0-7869-0697-9.
- Richard Baker, Ed Bonny, Travis Stout (February 2005). Lost Empires of Faerûn. (Wizards of the Coast), p. 124. ISBN 0-7869-3654-1.
- Ed Greenwood, et al (1989). Hall of Heroes. (TSR, Inc), p. 120. ISBN 0-88038-711-4.
- Steven E. Schend (1997). Lands of Intrigue: Book One: Tethyr. (TSR, Inc.), p. 67. ISBN 0-7869-0697-9.
- Steven E. Schend (1997). Lands of Intrigue: Book One: Tethyr. (TSR, Inc.), p. 8. ISBN 0-7869-0697-9.
- Steven E. Schend (1997). Lands of Intrigue: Book Three: Erlkazar & Folk of Intrigue. (TSR, Inc), p. 31. ISBN 0-7869-0697-9.
- Steven E. Schend (1997). Lands of Intrigue: Book One: Tethyr. (TSR, Inc.), p. 64. ISBN 0-7869-0697-9.
- Ed Greenwood, et al (1989). Hall of Heroes. (TSR, Inc), p. 119. ISBN 0-88038-711-4.