MLP/Undertale crossover.
Not a PWNY-verse story.

Long ago, the Monsters and Humans fought a great war. The Monsters lost, and were sealed in the Underground. It would take the power of seven human souls to break the barrier that kept them imprisoned. They only had six. And so the Monsters waited and hoped, praying that another human would find their way to the Underground. Some thought the seventh soul would give their King the strength to break the barrier. Some dreamed of a human who would be their friend, and save them all...or had nightmares of one who would bring back the war.

...but nobody came.

...but somepony did.

Eons after the war, with no way to tell how much time had passed above, a tiny blue filly with wings and horn fell into the underground, calling for her Mama. None knew the poor creature's nature or origins...but her soul was powerful with magic, even more so than a human soul.

None can know what will come...of this little 'Woona'.

Cover art by Sanyo21

A millennium ago, give or take, Princesses Celestia and Luna were nearly defeated by the most powerful villain that they had ever faced, Grogar, the dreaded lord of Tambelon. Thanks only to the whims of random chance, the two princesses survived that encounter, but have been forced to live in fear of the time of his inevitable return. That time is now...

...But whatever revival was intended has gone a little... wrong. Behind the wheels of Grogar's body is the spirit of a slightly extremely eccentric human. Equestria would have been lucky to survive the real Grogar, but will the ponies fare any better with this loon ruling Tambelon?

Sex Tag For Sexy Times Reasons, Gore Tag For Gorey Time Reasons.

You. Have. Been. Warned.