A unit that is cursed is more likely to suffer from afflictions due to damage. This effect can only be removed through the great expense of a wish spell.
This is not to be confused with the magic item trait of the same name, which prevents removal of the item after it is given to a commander.
Sources of this effect are Curse, Spirit Curse, Doom, Knife of the Damned, Sword of Aurgelmer, a unit trait called Death Curse that inflicts curse on the unit's killer, and another trait called Curse Bestower that inflicts curse on the unit's attacker if they fail an MR check. Notably the indie commander lizard shaman will use this spell liberally so it is recommended to avoid sending valuable units, like your pretender, to lizard provinces.