An important lesson in Demonic summoning

When I was young I noticed I had an affinity for performing magic, which impressed my family. They sent me off to be an apprentice to the village Mage, where I began honing my skills. Soon though I found I had a Talent for Necromancy after I revived a dog which had been trampled to death a few days earlier. Needless to say this wasn't exactly welcomed by the community and I was driven out at the age of 12. On my own I began honing my skills in my unnatural talent, eventually building a lair in a cave where I would raise the dead. I had no visions of using them to conquer anything, but I began offering my services to armies who wanted undead soldiers to help fuel their conquest. Years later I had grown well known amongst the unsavory, but rich from their coin. My once humble cave home now a complex dungeon of necromantic power. But still I had only studied the realms of Necromancy, and had never thought of going into Demonology.
Until I got an offer from a certain Pyromancer King, who promised me wealth I had never imagined if I were to summon him a monster from another realm. I figured at the time that summoning was gonna be as easy as necromancy, and I began acquiring as many books as I could. After months of studying, I figured I was ready.

I set up everything to perform the rites, drew all the right symbols, gathered the right incense for burning, and memorized the correct chants. I began, singing words of power in an ancient language, my lab full with the smell of burning herbs. The last part of the ceremony had me give a bit of blood, which I did by pricking my finger. Suddenly, a portal appeared above the symbols! I was knocked back by the force it create, hitting the wall behind me.

I gazed into the portal, only to see a mess of tentacles leave it. And there were many, and they were large. My initial excitement was cut short by a single thought: I had no idea how to control this thing. I tried giving it an order, but instead I was snatched by the legs by 2 of its tentacles. I tried fighting back, but its grip was too strong.
I dragged me much closer to the portal and held down my arms as well, making escape impossible. A 5th tentacle began stroking my chest, feeling me up for reasons then unknown. I was petrified out of fear, I couldn't scream or anything. Soon that tentacle stopped feeling up my chest, and instead went straight into my mouth.

The appendage plunged in and out of my mouth, whilst is moved around inside it. It seemed to excrete a strange fluid, which made me feel oddly aroused. While it violated my mouth, another tentacle came forth and began rubbing my feminine regions. I wriggled around trying partly to escape, and partly from the feeling of being touched. My juices began soaking through my robes, mixing with the strange substance being produced by the tentacular beast.

I felt the tentacle grip  on the edge of my robe and rip it off, leaving my nether-regions exposed. I could now feels its bumpy, slimy skin rubbing me. I tried moaning, by my mouth was still blocked by the tentacle. Suddenly, I felt the tentacle enter me! Being a necromancer means you often have trouble with men, so I was a virgin. I had never had something inside me, much less something this large! I let out muffled screams and moans as I felt it begin to ravage me from inside.
It was pumping in and out, vibrating and excreting it's strange goo. I was unsure of what to do, should I continue to fight back, or should I embrace what was happening?  I could feel my hips thrusting back and forth to the tentacles insertion, and I felt a feeling building up inside me. I closed my eyes and lay back, stopping my struggle.

I began feeling my hips bucking and my legs giving way, and suddenly I found myself overwhelmed by a feeling of extreme pleasure. I spasmed and moaned all over the floor whilst the tentacles continued to have their way with me.
Eventually the tentacles released a copious amount of their fluids into my mouth and vagina, and they left me, and retreated to the portal where it had closed. I stayed on the floor, mesmerized and exhausted, but something about the fluids still inside of me kept me aroused. I was still a bit loose from the insertion, so I stuck a few fingers in, and those few fingers soon turned into my whole fist. I spent an hour or so pleasuring myself, evidence of it soaking the floor. Eventually I passed out, and when I awoke, there stood the Pyromancer King and his men, expecting to find a summoned eldritch creature, but instead found somebody who was to become his new concubine.