The final boss of the game turned out to be a culmination of the unnamed monsters. They merged into a collective shadow dubbed "Legion". After two more playthroughs, Twilight beat the game on Seraph difficulty. Within a few days, she was ready to show her friends the secret she'd concealed within the game's code.
"Alright, guys. You ready to see what my deranged mind has in store?"
"SHOW US!" Pinkie screeched.
Twilight pulled up the options menu. She selected the gallery which displayed the custom art pieces from the game. There were even a few pieces that hadn't made it into the final cut.
"This is why our versions will different from the marketed ones. If I kept it in, I couldn't sell it anyway. If I tried, I'd be in deep shit. If I hold the control key down and type out the word "spouse", I can unlock a secondary gallery. It only works if I've beaten Seraph difficulty."
Rainbow's eyes became comically small and beady.
"It's...All porn...The fuck...!?"
"The internet likes to turn everything into porn. Figured I'd beat it to the punch this time. Kinda wondered if it'd take all the fun out of it for 'em. To tell you the truth, though, I've been drawing porn since I conceptualized the novel. In a way I was making fun of myself for being a total perv."
Rainbow stared her friend dead in the eye.
"...You better not keep this all to yourself."
"Now why would I do a thing like that? After all..."
Twilight smirked.
"I think you'll get better use out of it than me."