A Dolahan (sometimes spelled Dollahan) is a blackened suit of armor possessed and controlled by a demon. They can be killed by ordinary means, but are extremely strong, magically powerful, and never require rest. The Dolahan's strength is also its weakness, as a true Demon, it requires the protection of the armor to exist in the physical world. Hit it hard enough to knock the armor off, and the demon can be spoken out of existence by invoking the name of the One King.
Dolahans are mentioned in The Inclination to Destiny(Story) and The Reunion of the Eighth Power, as well as The Path to Ascension(Story). They are also a unit in mage Wars RPG and a card in the Mage Wars Card Game.
In The Reunion of the Eighth Power, a man is also seen wearing "Dollahan Armor" - the armor can be retrieved from a defeated dollahan and worn. It gives the wearer drastically enhanced speed and endurance, as well as unnaturally long life. It also cannot be removed, eventually growing into the wearer's flesh.
Anyone who puts on Dolahan armor will one day die in it, transforming first into a Thusen Draugr, and, eventually, when the flesh has rotted away entirely, back into a Dolahan.