(A MLP and W.I.T.C.H crossover)
Twilight has been having nightmares of late. Visons of four young mares trapped within the four elements of nature: Earth, Wind, Water, and Fire. The one constant in these nightmares is a voice that tells her to protect the heart. One day, she finds a young mare with the power over lighting, but without a clue to where she comes from. Just a name, Will.
The returns of an old enemy heralds a looming threat and a darkness that will eclipse them all. What is the connection between them, and what is the link between the mare and the visions.
What is the heart of worlds.