Eldanoth is shown here not just draining the soul but disintegrating the body together with it.
This way he will have no trouble went pretending to be the victim without people finding the soulless body he left behind.
The soul will be absorbed inside him, he will then gain all the memories from the victim to impersonate him perfectly. He will form a strong illusion over himself to look like the victim and lure away other people to take their souls.
this amazing artwork was made by http://www.furaffinity.net/user/synec/