SPOILER!!!!!!!!
He does die like life extinguished heart stopped, but he doesn't stay dead. Seriously dude read the book I HIGHLY suggest it. Back when he returned to the double gate where he first got his powers and then unlocked part of the memories of the original Shadow Monarch he also got a black heart (chapters 128-130). The original Shadow Monarch's heart was placed in his chest. It was so that the Shadow Monarch could take over his body, but that didn't happen (don't remember the exact reason why). So in the upcoming battle when his heart stops the "extra" black heart starts pupping and he basically becomes one with the original Shadow Monarch..... Honestly the book WAS really good, but the ending really left SO much to be desired. It was pretty ridiculous.
Me: *See's a spoiler alert*
Also me: meh, what could make it even worse-
Spoilers: "He's gonna die"
Me: *Tears up in regret*