Well, it's really simple. Death incarnate has a soul, and when a vessel is destroyed, his soul is free and moving. Unbound. The Abyss eats those types of souls. Game over. >=] Samething applies with Lazarus. He dies in one body in Mary's presence, he doesn't get to the other one. Of course this is implying Mary will be anywhere near the fight. I can promise you all of my characters are going to be nowhere near the death of Slyre. 

It's the perfect crime. >D 

And my logic makes sense. Just read the 'Others' tab of Slyre's relations.