For Rainbow Dash and Twilight Sparkle's latest date, they've decided to explore the Castle of the Two Sisters together. Rainbow hopes to find secret passages, traps, and treasures; Twilight wants to search the libraries for one-of-a-kind books and lost knowledge. Instead, in an abandoned chamber deep below the castle, they find a sanity-shattering horror, not meant for the eyes of mortal ponies!

Oh, and they also find a tentacle monster from another dimension.
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Fetish porn, of course, featuring: cum inflation; tentacle sex; spit-roasting; cum inflation; all-the-way-through; belly bulging; cum inflation; extreme insertion; implied cervical penetration; bumping and grinding; and cum inflation. Also, these fetishes might be considered spoilers: rape roleplay; consentacles.

This story was a commission from Anon #3.

2017 Feb 22: Added a slight bit before the clop, to make the subtext a little bit clearer.
2017 Mar 17: Name changed from "Green Sun".

Big shout-out to the folks on the Pony Inflation Thread in /trash/.