Succubus are Demons.
Stygian Furies are another type of monster with the same graphics.
ion Succubi have a chance to deal Magic damage. Succubi also cast several different curses.
Defense Curse If you have more Life than Mana, then they give you a curse that halves your defense (65% in Nightmare, 85% in Hell).
Blood Mana Succubi and Baal cast a special curse shown in the screenshot below (Along with Thunderstorm and Energy Shield). This curse causes you to do damage to yourself when you cast spells. For skills that require more mana, you will take more damage. This even includes such spells like Teleport but doesn't include Thunderstorm or Energy Shield because you have already have cast them. Whenever this curse is cast on you, stop casting spells until it's worn off, click on a Shrine to counteract it, or go back to town and have it removed. Blood Mana only affects you if you have more Mana than Life. If you have at least as much max Mana as max Life, you can be cursed.