You look terrible, monstrous and frightening.You are obviously unusual and anyone versed in such things can spot that you are one of the Creatures of the night. Even Entities can have this flaw, as absolute good seems terrible to ordinary mortals. More common examples include walking corpses, ogres, ghosts and so on.
You cannot use any social skills on ordinary people except to frighten them.
This is the standard weakness, that almost all supernatural creatures have. The standard way to get around it is to have Transformation.
There is a bonus to Terrible Form; you can scare people even if you lack Intimidation, using your Powers action value. This only works once, and not against people used to having monsters around, such as monster hunters and other supernatural creatures.