The flower of Necronia

Alan bent down and scrutinized the dead vegetation.

When he saw the fine pink powder almost undetectable if you didn't know what to look for, he had no doubts as to what had killed all the vegetation.

Axel had already explained everything he knew about this dungeon to him and together they had deduced that the boss of that dungeon must be a Vampire.

They were Superior Demons and that would explain why Kevin had been hypnotized.

Indeed, Vampires were well known to be able to enter your mind and hypnotize you, and what they enjoyed the most to do was making the humans who had dared to disturb them in their nest fight against each other.

In addition, the Vampires between them reproduced very quickly, it took only 15 days for their female to give birth and only 60 days for them to become adults, that's why the number of demons to kill was so high in Kevin's quest.