Concubi are winged fiends who prey on mortal suffering, and are one form of immortal spirit that are native to Mabar. They are spirits of murder and despair, embodying emotional pain and loss. They are known for preying on mortals, corrupting them with temptation before causing them to lose everything, feeding on the suffering. In Mabar, they victimise the other denizens of the plane, targetting other immortals as well as mortal hostages. The suffering of a fiend is just as satisfying to them as the pain of a mortal. The few concubi on Eberron are generally agents of the Lords of Dust, the most notable of which is Thelestes, the Velvet Blade.
Concubi, sometimes referred to as Incubi or Succubi, are accomplished shapeshifters. Their natural form appears humanoid, with leathery wings and clawed digits, but they are rarely seen in their natural form. Though mortals have come to recognise these spirits via the names Incubus and Succubus, the distinction is irrelevant as Concubi are able to shapeshift into either sex.