One night on the road to Canterlot, Trixie comes across a creature made of metal and flesh. She proceeds to engage in an awkward conversation with him involving secret missions, powerful evils, and hugs.

Crossover with Bionicle.

This story is a sequel to My Little Bionicle: Destiny is Magic

Twilight and her friends have been sent to Mane Nui to help the Toa Mata to save the island and the villagers. Meanwhile things are happening in the land of Equestria, Shades are appearing in Ponyville and a strange armor green pony has been seen with the Great and Powerful Trixie. The Order of the makuta have not been seen since the Mane six freed Artimes. And who is this unknown figure seen wondering the Frozen north.

On the Island of Mane Nui, Six heroes shall raise to face a long forgotten. With the great masks as their guide they are destined to change the world. Meanwhile Twilight, her friends, and the princesses try and solve the mystery of Six stars only seen when Luna first became Nightmare Moon.

Note: AU. Bionicle in the MLP universe

After a 1000 year wait, Turaga Vakama awakes from a vision that tells him Tahu and the five other toa will not be coming to rescue his island after all. As he goes to tell his villagers the terrible news, Vakama's captain of the guard tells him that Rainbow Dash, Toa of Loyalty, is already here, and is 20% cooler than the legends predicted. Vakama is skeptic about the new arrival, a creature the likes of which he's never seen before. Determined to prove Rainbow and her friends as frauds, Vakama pits the Mane 6 against the evil Makuta, master of shadows. Whether the magic of friendship can overcome this dark foe remains to be seen, as the battle for the fates of the Great Spirit and the equestians Princesses begins. (Note: This fic assumes little-to-no prior knowledge of the BIONICLE storyline. Every necessary detail will be explained as it comes up.)

The world of Equestria has lived in peace, never knowing that this world was never their home to begin with. Now when their six protectors go missing they must call upon five misfits. Each of them have a sordid past with each of The Elements but they must put those behind as they enter an new world that at the same time seems so familiar. They must tread carefully, however, for the shadow of The Makuta knows no bounds. Even for those who thought themselves protected.

Co-written with Fernrisian Brony.

While journeying between dimensions to try and warn the Toa Nuva of possible doom, Takanuva, the Toa that controls both light and shadow, finds himself in a world of purely organic and powerful beings known as ponies. Now he must find a way to leave this universe and continue toward Karda Nui. But there's something else in Equestria that shouldn't be, and a Toa may be just what is needed.

Takes place after Takanuva's Journey, The Kingdom, and Dark Mirror, but before The Final Battle.
The story takes a lot from the Bionicle storyline, particularly that of 2008. If anything confuses you, I recommend the amazing resource of biosector01.com.

After an accident with the Kanohi Olmak, Takanuva finds himself stranded in a new dimension and stuck in a new form. With no way to get home to his own universe, he has resigned himself to living out a peaceful existence in his new home, but his past will soon catch up to him in a way that could be disastrous for not just his world, but for all of them.

Before they could complete their mission, and rescue the last of the Matoran, the Toa once again attempted to vanquish their old foe, the Makuta, after he escaped from his prison. Instead of standing, the Makuta fled, prompting the Toa to follow, and step into a world unlike any they had ever seen before.

Set after the Web of Shadows, but before the Mask of light.
Characters and tags will be added later
If you dislike the story, please tell me why in the comment section. I can only be as good as my feedback allows me to be.
Note, I am basing 99% of my knowledge off the films.