Frisky Cho'Gath

It was a serious time, an entire section of the league had been red-lit and sealed off. One of the amateur summoners had failed to properly bind the monstrous Void creature, Cho'Gath, who took to rampaging around in his freedom, razing anything in his path to the ground. The magical foundations of the League ensured he would not breach the outside world, but he was certainly making a mess of the inside.
Compounding the matter, not only was there irreparable damage being done to league equipment, there were a handful of summoners, trapped with the beast. Consulting the Grand Magus yielded a distressing solution. The monster could be summoned into another wing, to attempt control there or the monster could be left alone, the entire wing serving as it's containment- the other summoners be damned. The only other hope they had, was that the amateur summoners would stay alive and earn their wings, by containing the monster on their own.

It had been a rough start, but the summoners eventually banded together, and hid away from the beast. They devoted their time and energy to their arcane books, desperately hoping to understand the complex requirements for a containment spell. The trouble was the powerful enchantments they needed to invoke required five summoners to work together, to seal the beast away. Following this path of reading only led to the same answer, time and time again, until one of the summoners found a bypass. It required considerable sacrifice, but it would save the group. She stood up and gave the instructions to the other summoners, who quickly set to adorning her body with symbols, turning her into a walking rune.
The girl, stark naked and covered in a language older than her walked, determined, to the creature, who was immediately aware of her presence. Staring her down, he was intrigued, until she began to invoke the ritual. It drove the monster into a frenzy and he quickly stomped on the ground, a web of void spikes lashing out and holding the girl firmly in place. Shaken, but not dissuaded the girl continued her recitation, the runes beginning to react to her calls. Savagely, the beast grabbed hold of her, and impaled her on his void cock. Silent for a moment, the girl wheezed in pain, grabbing hold of her stomach as the beast began to rape her open. Refusing to give up, however the girl continued the incantation, between grunts, and pained moans. Finally, after a long struggle, the rite was complete and the monster was sealed away. Not before he filled her with his load, though. The girl lay there, trembling and in pain, a nauseating warmth coming from her belly as her fellows ran to her, the sounds of lock down lifting in the background. A team of more experienced summoners rushed in, taking the damaged girl away to the infirmary, where she would later be brought back to perfect health.
Not before she mad an important choice, though. Laying there, goo leaking out of her and utterly exhausted, she thought to herself.
"I've definitely found my new main. Cho'gath OP."