Help in warlock

Hello, I've been playing for 3 days and my character is a warlock, I took Demonology specialty and they gave me an attack called Metamorphosis in which I become a demon using demonic fury, up there well.
I do not know if it is a bug or not but the attack makes me become a demon without more, and also the description of the attack says that increases the damage inflicted by 0.00%, someone explains what the attack is or if it is a error or something?
Thanks in advance!
And sorry my bad english :(