Defilers refer to iconoclasts that stains, vandalise or destroy a site, an area considered as "sacred" in a religious, political or symbolic way. This type of villain acts to desecrate its target and make it unworthy of its meaning, attacking a very symbol or value through its representation, and is in some ways similar to a sacrilege.
Defilers attacks a value that they consider as heretical, sinful, insulting or even responsible of their woes, with the intent of taking it down, thus relating to fanatics, violent anarchists or even protestors and rioters, but their actions are almost always exceedingly disrespectful if not downright violent.
Some examples would include fanatics who paint racist symbols in religious graveyards, people who burn or vandalize churches and temples in religious wars, "revolutionaries" who burn down flags, and so on and so forth. Defilers are known to have a bad habit of not respecting something that is concidered sacred or greatly valued, often for unjustifyable and hardly reasonable means. Sometimes they can also either be business goings persons that view a sacred object as a threat to profits, also if they value and/or dispise a certain person that is considered sacred and want to either make them a means to empower their own business or to alltogather be rid of them, or they can plain and slimpy be demons or dark gods, which are infamous of having no love or value for mortals and everything to do with them in general, neither to their rules, their customs, and often what is considered moraly right.