Word of Nurturing, Greater

Level: 6
Duration: 5 rounds (normal) or instantaneous and concentration, up to 1 round (reverse)
Saving Throw: None
Normal: With this powerful utterance, you remind the universe of your ally’s true physical form, and even his most terrible wounds begin to knit together.
Your target emits a greenish glow from within (equivalent to a torch’s light). You grant a creature fast healing 20. 
Reverse: Great gashes and terrible wounds tear at your enemy’s body, causing massive bleeding and terrible pain. 
You unmake a portion of the subject’s being as you utter the reverse form of the life-giving words. You deal 10d6 points of damage to the subject. If you concentrate for 1 round (a standard action), and the subject remains within range, it takes another 10d6 points of damage at the end of your next turn.