Sunset Shimmer and Twilight Sparkle have one thing in common: They've both been overwhelmed by Equestrian magic, transformed into demonic forms. That's something that's pretty hard to put behind you.
Princess Luna may have a solution. A spell that will allow them to communicate with their demonic selves inside their heads, through dreams. Both are nervous about the prospect. Who wouldn't be?
Sunset and Sci-Twi vectors courtesy of Emeraldblast63 and Givralix.