A simple spell. That's all Twilight thought it was after finding a strange spell called the "Xen portal" in a spell book somepony left on her doorstep, but something has gone wrong. Something has gone so so wrong. These monsters, these things, are appearing in Ponyville, attacking and killing anything they can. Now Twilight, armed with whatever she can find and with the few allies she has, must kill these creatures and find out how to close the portal she accidentally opened before all of Equestria is doomed.

A My Little pony/Half Life Crossover set in an alternate timeline before the events of "Magical Mystery Cure."