"...in peace the sisters reign, and the world is divided between them. When care, or woe, or wan disease, steals for a time the mortal from his allegiance to the calm and blue-eyed Sleep, then do the sisters ply their magic arts to win him back again, and, by their soothing influence, lull him to rest once more, and again unlock the portals of the palace of dreams..." (from the bands website)
Read more: http://www.sevensistersofsleep.com/