Out of countless Souls, ten were chosen to be reborn as Monsters into the Higher World. 
A World much different than ours, filled with Demons, Devils, and Mythical Creatures.
Ten Chosen Souls, Ten Chosen Candidates. For what they are Candidates, remains a mystery. 
"Weaklings shouldn't worry about such things."
Indeed, only the strong can survive, which is why, for ten Candidates, ten Dungeons were built. 
Raise your strength, get used to how things operate in a World of Monsters, and perhaps you, then, will be worthy of the answers you seek.
One of those Candidates had been given, in his previous life, the name Mark. 
But such a name doesn't mean much. 
After all, he is, in this Higher World, better known by his Titles.
The Devourer & The Evolving Monster.

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Chapter 355 - The One To Blame Is...