My interpretation is that you never died, you were dying and would have expired without immediate aid, but the Dragon Rider was distracted before he could finish you off.
And as for "just kill 12-year-old duke", I actually believe that you could NOT do that until after becoming the Divine. The Demon of Lies has a piece of the soul of a GOD. You needed to become a demigod yourself just to be on even footing with it. Alone, you would stand no chance. (Look how it shut down Zandalor in the Council of Seven.)
