"I know why you're here," the old man says. He is sitting at the back of the club, still wrapped in a shawl despite the roaring fire behind him. He doesn't bother to turn, instead staring into the flickering flames as he sips a glass of brandy.

"I've seen that look before, that hunger. You think you've exhausted every pleasure this world has to offer and you're looking for some new thrill to ease the tedium. Then you heard about them and you wondered if it was possible, without dying and having your soul sucked out that is. Then someone told you about me."

He stops to swirl the liquid in his glass.

"It's true," he continues, "the rumours. I fucked a succubus and lived to tell the tale."

He takes another sip of the brandy.

"Is it? Yes, that's always the first question they ask. You always want to know what it's like before the how. Is it the ultimate sexual pleasure? I can see you thinking that from the hunger in your eyes. It is, or at least I have encountered none better."

The man shivers, despite the heat of the fire and drains the contents of his glass.

"You'll need the Masterton Covenant."

He produces a flask from under his shawl and refills his glass.

"Don't trust them here," he explains, "Too many enemies."

He takes a sip from the refilled glass and continues his story.

"There is a Hell of sorts that occupies a plane of existence adjacent to our own. With the right knowledge a person can cross the barrier between both planes. Some even have the knowledge to make it back. The beings that exist in that plane, the denizens of Hell, or demons if you will, regard us as little more than cattle or playthings. To us they seem as much as gods as a farmer would seem to his livestock.

"It is possible to control them though, the demons. For all their power their existence is constrained by a set of rules and conditions far beyond our understanding. They are compelled to enter into contracts with us and always keep to them. Some have speculated this is because they were once angels created to watch over and serve us. I can't answer whether this is true or not, all I know is that a demon will never ever break a contract with a human.

"So it's easy, I can see you thinking. Perform the right ritual, word your bargain in the correct manner and nothing can go wrong."

The old man chuckles.

"Many thought the same thing. They summoned demons into this plane to serve them or even travelled into the demon's realm and thought themselves safe through the bargains they had created. And in nearly every case they eventually lost both their life and their soul.

"A demon will never break a contract directly, but that doesn't mean there aren't loopholes.

"You can command a demon not to kill you, but it is still free to drive you insane, or imprison you for eternity.

"You might command a succubus not to hurt you, but what use is that. She will kill you and you will be in absolute bliss for the whole time."

The old man shivers again, although it is hard to tell whether this is from fear or some other emotion.

"That was until Clive Masterton. Masterton was a mathematician primarily interested in logic. Rather than use the clever words so favoured by lawyers he looked instead to pure mathematics. His contract was not a piece of English but a complex series of logical equations. It was completely unbreakable. None of the demons Masterton summoned to serve him could ever harm him, his relations or his loved ones. Still, Masterton was cautious enough to never hold them here for too long or ask for too much.

"I can give you the exact text of Masterton's Covenant, but before you continue with your endeavours I would ask you to indulge the wishes of an old man. Hear my tale first and decide for yourself whether the thrill you seek still comes without a price."

The man takes a large gulp of brandy as he readies himself.

"When I was young, like yourself, I too had attained a level of knowledge that made my life very comfortable indeed. However there are only so many girls you can bed before the lack of challenge starts to become tedious. Being able to obtain virtually anything I wanted did nothing to assuage my boredom. I was eager for new thrills.

"While attaining my knowledge I read about succubi. These demons, along with their male counterparts the incubi, are the avatars for the sin of lust. They are said to be the embodiment of sexual perfection. Over the centuries many a man of knowledge has attempted to summon a succubus in order to gratify carnal desires.

"It is a highly dangerous act, for a succubus is also a vampire. She drains her victim, often completely, of their life force during the act of sex. Still, I wanted to experience such an exquisite creature. What greater thrill can there be than risking one's life and soul in pursuit of the ultimate sexual gratification?

"Most contracts are useless with succubi. Once in their arms men will sign over everything — their life, their soul — just to prolong the pleasure. Most revoke the very contracts they bargained for their protection.

"The Masterton Covenant cannot be revoked."

The man pauses then, lost in contemplation as he stares into the flickering flames.

"As well as being governed by arcane and unfathomable laws, the denizens of Hell also conform to a strict hierarchy. The succubus I had chosen — I dare not utter her name even now, even as a whisper, in case she should hear — occupies a high ranking position. In my arrogance I had determined that rutting with a mere minor minion on the fields of forbidden pleasures was beneath me. Instead I was summoned to the sumptuous private chamber of a major succubus. The walls of her chamber were covered in black velvet and studded with erotic paintings. Candles filled the room with soft light and trails of perfumed smoke. A giant circular bed took up nearly half of the room and was piled with cushions. I barely noticed any of this. The succubus sat on a silver chair beside the bed and captivated my attention completely.

"They are exquisite; words cannot truly describe them and she was elite amongst her kind. She was taller than most men and her body was perfectly proportioned apart from her breasts. They were large and full, but not grotesquely so. She was a Playboy fantasy with no need for the silicone. Jet-black hair cascaded around her shoulders in wavy curves.

"There could be no mistaking her for human though. Her skin was a deep blood red, her eyes were two bottomless black pools and there were two tiny horns upon her head. These features only seemed to heighten her appeal though. They reminded me of what she truly was and it only added to the thrill of the danger.

"She was completely naked and without shame. She sat and watched me with an amused expression, legs spread wide to reveal the slit of her naked pussy. The flesh around it was smooth and hairless.

"'What would you like, little human?' she purred.

"Between her legs the slit of her pussy opened for a few brief tantalising moments like lips beckoning for a kiss.

"'You, ' I replied. 'For one night of pleasure.'

"'Mmm, ' her eyes still twinkled with that look of feral amusement. 'And what will you pay me?'

"'The seed which you take from me and enough of my life force that can be replenished with no further damage to both my body and soul.'

"'I can take them anyway, but it is so much more pleasurable when they are freely offered.' She stood up out of her chair. 'Any conditions before we begin?'

"I began to recite the Masterton Covenant. It is a series of statements that forbid the demon from inflicting any lasting damage on the bargainer's mind, soul or body either now or in revenge at any time in the future. All of them are written not in words but pure, unambiguous mathematical logic."

The man turns with an impish expression on his face.

"It can take a long time to recite.

"The succubus at first looked amused, then puzzled and then finally blank. This is the point when you can see them thinking, running their mind along the hard lines and angles of logic in search of a weak point or a flaw they can use to turn the bargain in their favour. Eventually she hissed in anger when she realised there was none, but it was useless, as I've told you already, they are compelled to accept our contracts even if the terms are bad for them.

"'Very clever little human, ' she said, her face now cold and aloof. 'I will give you your night of pleasure and return you, whole and intact, to your place of origin.'

"It had worked. Smiling cockily I beckoned to her bed. 'Shall we begin, ' I said, brimming with brashness.

"She moved faster than I could react and was far far stronger than her slim form suggested. I was a big man back then, not this withered shell you see now, and she lifted me up and threw me down onto her bed as if I was nothing more than a doll. Within a flash she was astride me and her sharp black claws had ripped away my clothes. Her ferocity caught me off guard and I was gripped by a real fear. What if I'd been wrong?

"'Your bargain will preserve your life, but do not presume you can give orders to a succubus on her own bed, ' she said.