SPOILER!: This contains lore and what the Warframes really are. If you haven't played the Second Dream quest and don't want to be spoilt, do not read until you complete it.

My name is Karn, it's been over one-thousand years since I became a Tenno.

I've faced all sorts of horrors and challenges.
The grineer, a race of clones, seeking out others to stabilize their own DNA and hating anything or anyone not like them.
The corpus, a conglomeration of commercial and industrial interests, they acquire Orokin technologies and warframes to trade and sell using any means necessary.
The Infested, an ancient plague created by the Orokin to combat the 'Sentients' but has spread throughout the system.

Me and the new Tenno Greavus who uses the new Nekros warframe were sent to assassinate a grineer general, but Greavus struck a deal with the grineer and left me within the ship while the grineer tried to take my warframe for experimenting. Long story short, they failed.

I barely managed to escape to the void in an attempt to take down Greavus, but my Orbiter and Liset are damaged during flight.

My Orbiter exits the void right above a bright planet. With its engines down, the ship crashes right into a city on a mountain during an invasion.

I arm myself and leave the Orbiter, but for the first time in centuries, I'm not prepared for what greeted me... Small colourful equines.

Warframe/MLP crossover, image is my rhino warframe and the one used in the story.

Twilight's clone barely escaped her grisly end, and is seeking refuge in the large city of Manehattan. She's quite fine with going it alone, until she spots somepony just like her.

Inspired by the Cover Art by Badumsquish

In a remote corner of the Solana Galaxy lies a backwater planet called Veldin. Nothing important ever happens there. Nothing exciting, either. Ratchet, a Lombax with no idea of his origins, is beginning to grow bored with his life, and dreams of excitement. He wishes on a falling star for some excitement to find its way into his life.

The falling star answers by crashing into his home in the form of a basket carrying a tiny creature with a horn, a pair of wings, and four hooves. The name on the basket reads "Twilight Sparkle".
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Part of the PWNY-verse.

Edit: Now with cover art by the amazing G_Haze
Video Consultant/Technician: m2pt5 (he provides the infobot videos and similar.)

Edit: Game Timeline
Ratchet and Clank: Done
Going Commando: Done
Up Your Arsenal: Done
Deadlocked: Done.
Size Matters: Done.
Tools of Destruction: Done.
Quest for Booty: Done.
Crack in Time: Done.
All 4 One: Done.
Into the Nexus: Done.

Raven of the Teen Titans has long been a closet pegasister. She was introduced to Friendship is Magic by Beast Boy and Starfire and - although she is loathe to admit it - she enjoyed it. She especially identified with the character of Twilight Sparkle. What with Twilight's enjoyment of reading, talent in magic, and unexpected but life changing friendships, it felt like Raven's own life mirrored and sugarcoated onto a world of pastel colored ponies. Even Twilight's friends reminded Raven of her own to a certain extent.
When she wakes up one morning in Twilight Sparkle's body with no idea how this happened or how to fix it, she begins to think she identified with her a little too well.
Now trapped in the plot of the series from the beginning, she has to find away to fix this, find out what happened to the real Twilight, and at the same time save all of Equestria. At least she has some friends to help, right?

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Crossover idea inspired by the fact that these two characters share the same voice actor, Tara Strong. Originally, it was just an idea I played with for fun, but I have a serious - and frightening - plot for it. Dark for later chapters.

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