Mystic nightmares

Equipped creature recieves a -1/-1
per round until either the creature dies
or artifact destroyed.
If placed on a friendly creature, it recieves a -1/-1 per round till dead. Upon death can return to hand or move to next creature. (Once only) each round on your creature the book recieves a +1 to either of
the following: increase to X/0 or 0/X or
deal stored damage to chosen player