Owing to his great absentmindedness and poor memory, Parwyyd hired Dunstanny to assist him in his work. Dunstanny organized his library, carried his books, and kept track of which spells Parwyyd had studied each day and which he had cast, as he soon forgot even that. Dunstanny even knew the details of each spell, their dimensions and effects, and could suggest to Parwyyd the ideal spell to cast in any given situation. He even alerted Parwyyd to danger when he was distracted or deep in thought, and defended him when he had to.
Dunstanny felt it was an honor to serve Parwyyd, the most brilliant wizard he knew, with his assistance allowing the mage's mind to wander far.
In the Year of the Prince, 1357 DR, Parwyyd's tower was besieged by a force armed with catapults. The Great Door once built by Parwyyd had been opened, disgorging monsters and the attackers believed that killing him would close it. As Dunstanny tried to maintain the library, he suggested that Parwyyd employ an incendiary cloud spell, which quickly drove the attackers off.
Dunstanny later accompanied Parwyyd to the Great Door, to which he had lured Kyriani Agrivar, and with her Onyx the Invincible. Dunstanny defended Parwyyd from an irate Onyx, nimbly evading and tripping the battle-hardened dwarf, and suggested a web spell to end the fight. He counselled Kyriani on Parwyyd's plan to close the Door, and Onyx on what the Door was doing and on Kyriani splitting into Kilili and Cybriana. He later advised Parwyyd to use a forked lightning bolt to eliminate the front line of gargoyles and kenkus that emerged from the Door, before suggesting he approach a fire elemental and use it as a fire source for a pyrotechnics spell, the fireworks dazzling the remaining flying creatures. Finally, he reminded Parwyyd to use telekinesis to close the Great Door, thus slaying the one who waits who'd seized control of it, and disintegrate to destroy the Door itself.