The succubus/incubus is one of the most dangerous low level creatures in the Dungeons and Dragons Monster Manual. I spend a lot of time evaluating the combat effectiveness of monsters. For reasons. It took me a while to figure out how to use them well, but they can turn a fight into a nasty mess for you players, as long as the dice roll in your favor.
These nasties aren’t of much use in a stand-up fight. Since they only get one claw attack in they don’t deal a lot of damage. That combined with 15 AC isn’t terrible for a CR 4 monster, but they’re not really heavy hitters.
The true beauty of these monsters is there Charm action, combined with their Telepathic Bond ability and Etherealness. The charm action has a DC 15 Wisdom save, which is pretty good at lower levels. If you can fit few of these creatures into an encounter, you’ll have a pretty good chance at getting at least one party member. From there, you’re going to want to get some distance and dip into the ethereal plane on your next turn.
A Succubus Can be Sooo Charming!
Normally, changing planes would block the charmer’s ability to command the target, but with Telepathic Bond, the succubi/incubi will still be able to direct the actions of the charmed player. In an encounter, turning one ally into a foe shifts the balance of the combat in a major way. And you get to watch the PCs try to hurt their friend only enough to give them a chance at saving without putting their life in danger.
Of course, I don’t think the Succubus/Incubus was supposed to be very dangerous in combat. They work best as infiltrators. In a campaign they can serve as a reason for a leader to have become corrupt and ineffective. They can also turn the party member against each other. Your rogue friend visits a brothel and gets more than he bargained for. Or perhaps your cleric takes some time to meditate in solitude; they come back thinking they’ve really gotten closer to their god. That PCs new friend uses them to lead the party into danger. The fiend then uses Draining Kiss to reduce the maximum HP of the PC in their thrall. Now you go into combat with the party’s cohesion damaged and one of the PC’s badly damaged.
Now get out there and hurt some PCs for me!