Diabel (i'm assuming) became a devil to help Anaya.
He make a contract with her that she will devour her soul in the end of her revenge. But if he dies before the contract can be fufill, she is free.
He may give a hint that his plans is to free her by dying. Giving everything she wanted, because he loved her from the previous life and was willing to sacrifice everything for her, even his soul.
That is the oposite of Erez kind of love, usurping her from everything to became her only world. (in the previous life, it was hint he did that when he offered mercy in the prision and in this life he was doing the same trying to kill Diabel by influence of the other devil)
Yeah, english is my third language actually, and it don't help that I'm sick too, so thinking in english became hard...