"From the beginning, your mission was destined to fail."
Azeuph, the Destroyer of Children is one of the Genius monsters and appeared on the Western Europe server after the Catastrophe struck. The girl seen in the image is actually just one of its host bodies and puppets, and its true body is the mass of flesh and eyeballs.
In order to gather Empathiom, Azeuph attacks and kills a Lander child, then possesses the body and merges its ki with the child's, preventing the body from disappearing. It then travels to a remote location, typically a cave or another enclosed area. When the child's worried parents or guardians inevitably seek out an Adventurer's help in locating the missing child, it leaves out hints as to where it is located, in hopes of luring out a raid party. When they find it, Azeuph pretends that its attacking the child (whose status screen reads that its still a Lander, not a monster) and makes it appear as though the raid would require them to defend the host body. After getting the child to safety, they would continue to battle the monster, only for Azeuph to reveal its true powers, using the host to attack its rescuers with a power beyond what they'd expected and slay them.
Although the host body is usually killed in the process, it only furthers Azeuph's plan; because a portion of the child's soul was still retained in the body as a result of being merged with Azeuph, the child's pain and anguish only amplifies the amount of empathiom generated by its death. And, in the chaos created by the reveal, a portion of Azeuph is able to slip away, preventing it from being killed by the Adventurers.
However, there is also a downside to this strategy. Because it merges with the child, a portion of it is still inevitably killed when the child is killed. Also, only a portion of it can escape during the distraction, thus decreasing its power even further. As a result, Azeuph has to wait to recover for a relatively long time, especially if the plan doesn't go as well as expected. Later on, as Azeuph reveals to fellow Genius Halacho that it is beginning to feel the childrens' emotions as a side-effect of merging with them.
Image credit: Psychic Hearts