deci is a mentally unstable person.

while his underlying morals are generally good, his methods for achieving good are twisted, full of deceit and even cruel. and when its all said and done, his ends NOT justify the evil means. seths methods tend cause more problems then they solve.

he is overly arrogant. do not insult his intelligence or especially call him crazy, he will be furious and try to set you "straight".

deci possess an invisibility cloak. one of his favorite ways to use the cloak is to "haunt" people with it. or more specifically, forcibly drive people to insanity to the point where they can no longer function or act in a way that deci desires. heres an example: deci wants a king to think he has a really bad memory. so deci sneaks into the kings quarters and misplaces objects. he forges writings in the kings handwriting and places them in the kings quarters (to make the king think he wrote them but forgot about them.) . doing things like this may cause the king to start to question his memory.
this is just one example of "haunting".