A burst of foreign energy has made it's way to Equestria and it's turning ordinary things into youkai (well…it's creating youkai too). Tons of spirits and phantoms spiral everywhere and all the energy and youkai and spirits, seem to come from one unnatural forest that frightens people, the Everfree Forest. Deciding to put an end to this nonsense (and annoyance to Erin), Erin Starlight, an immortal, lunarian, makes her way into the Everfree Forest. Of course, she's not the only one to investigate this incident…