This hulking Quaggoth is the most menacing-looking
prisoner in the slave pens, and the other prisoners
give him a wide berth. If any of the characters speak to
him, however, the Quaggoth replies in urbane Elvish.
He explains that he is not, in fact, a Quaggoth, but a
gold elf prince polymorphed into Quaggoth form by a
curse. He claims to be Prince Derendil of the kingdom
of Nelrindenvane in the High Forest. His crown was
usurped by the evil wizard Terrestor, who trapped him
in this form and exiled him from his people.
Although Derendil behaves like the highborn prince
he believes himself to be, he responds to stress—and
particularly threats—like a Quaggoth: violently tearing
foes limb from limb and rending their flesh with sharp
claws and teeth. He comes back to himself only after
battle, or when someone reinforces his “true identity”
to snap him out of it. Derendil laments that he is
slowly but surely losing himself to the savagery of his
Quaggoth form.
In fact, Derendil is simply mad, touched by the
delusions of the demon lord Fraz-Urb'luu. The kingdom of
Nelrindenvane doesn’t exist, and all of “Derendil’s”
recollections and personality are an illusion created by
the Demon Prince of Deception. The Quaggoth refuses
to believe the truth, and any incontrovertible evidence as
to his real nature sends him into a murderous rage.