DM tip: If you're in trouble, give the players a magical mcguffin you can bring back into the story later.
In this case, I gave one of my players a magical book that played pornographic scenes of yourself with succubi, complete with sound, whenever you opened it. He had some fun roleplaying with the item, but the real kicker was a whammy hidden in the history of the book itself.
See, the dragon that kidnapped the group's cleric revealed in passing that the book was given to him as a gift by Nocticula after "a hundred year weekend" they'd spent together. Nocticula, of course, being the demon queen of succubi.
The player of the cleric, who hadn't yet finished building their backup, was given an NPC next session to play instead. The NPC in question was a noble knight who had been rescued by the cleric in a previous story arc, his crippled body made whole by the cleric's magic, and who swore to defend her with his life and basically just followed her around as a mini-cohort.
So now the player gets to roleplay out the noble knight's grief that he'd never confessed his love, how much he regrets leaving her even when she'd admitted wanting to stay of her own free will, and how badly he wished to rescue her.
AHA! I cry to myself as the DM, rubbing my hands together with glee.
Enter the magic porn book once more. Only this time, it's leaking smoke and hot to the touch. The owner of the book checks it, discovers abyssal words appearing in burning script on its pages, and of his own free will takes it to the party's language expert, who's comforting the heartbroken knight. The text is translated, in front of the knight:
"What price would you pay to rescue her?"
The knight grabs the book and gets a glimpse of seductive feminine eyes and a sharp-toothed lascivious smirk staring out from the book's pages, words whispered into his ear as if from someone standing right behind him how he could gain the power to slay the dragon if he wished.
Then the rest of the adventurers tackle him to the ground and rip the book out of his hands, screaming bloody murder about deals with demons.
Of course, there's a dream sequence that evening, where the knight gets visions of him and all his allies being slaughtered in combat against the dragon, then an identical dream where he single-handedly defeats the dragon using a longsword that blazes with holy power and a shield bearing the glowing holy symbol of the cleric's deity.
There then follows a great byplay where the knight, waking earlier than everyone else from his restless dreams, steals the book from another player of his own free will. I even give the knight and the other player skill rolls to determine whether the heist gets pulled off successfully.
I shit you not, the knight rolls a natural 20, the other player a natural 1.
With that kind of result, nobody at the table dares argue the outcome. Roleplay is one thing, but when the dice are rolled, the results are sacred. Fate decrees the knight gets the book, whereupon he absconds with proper haste and gets intimate with a demon lord.
I must say I think I gave an amazing portrayal of the queen of all succubi. Specifically, her offer to the noble knight to grant him weapons to slay the dragon, and a hundred years and a day of joy and happiness with his love, if he agreed to her pact. He rightly questions her about her motives, and she goes from seductive temptress to apocalyptic rage when she screams in fury about the dragon scorning her. Apparently it's not a great idea to use a gift given to you as a memento of love by the queen of the succubi as a distraction when you're making moves on somebody else.
The knight gets the offer: power and happiness, all in exchange for one simple price. Their firstborn child.
He takes the bait, hook, line and sinker.
The knight pulls a longsword and shield out of the book, the ones that appeared in his dream. An abyssal mark appears seared into his palm as he draws the sword, a drop of his blood falling and soaking into the book's page. Demonic laughter rings out and a resounding voice decrees the pact sealed.
The best part of all this is that I had absolutely no plan or idea before the session started that any of this would happen. I made up all of this flying by the seat of my pants the entire time, but the entire table played into the events exactly like I'd predicted they would, an amazing spot of luck with some dice rolls backed up the trickiest part, and by the end of the night everyone's looking at me like I'm the craftiest god-damned bastard of all time.
Great session, overall.