The Titan's Heart. The Sleeping King Trilogy, #3

To save the world, one man must cease to exist. The truth is finally revealed: both tyrants feed on the Titan's Heart, an ancient magical construct that sustains all reality. As long as they live, they drain it, bringing the world closer to complete dissolution. The only solution requires the ultimate sacrifice - someone must undergo a ritual that will dissolve their consciousness into the Heart itself, becoming one with the magic that holds existence together.
Finn Ashwood, a street thief who never asked to be a hero, faces an impossible choice. As armies clash in the final battle between Aregor's empire and Maltherion's Legion, Finn and a small band of companions race toward the Deep Beneath, where the ritual awaits. But this is no clean death - it's a conscious dissolution that will scatter his awareness across all magic, all time, all reality. The world barely knows he exists.
He may be the only one who can save it.