Neo Pikachu said:
They're okay in moderation. As long as their presence in a fic is understandable and justified, then its fine. Like in the movies, the legendaries have stories behind them. If you're going to put them in your fic, make sure they have their own story too. But if they appear randomly when the really have no reason to be there, that's not good. Heck, that's not good even with normal Pokemon.
It all depends on the use and reasoning behind their placement. But they can be very effective to plotlines if used correctly and realistically.
Agreed.
In my fanfiction, I have some of the legendaries, but there are stories behind them and a insane-mind-blowing-virus to add to their appearances in many situations. For example, contrary to popular belief, I sometimes give the legendaries titles (for example; Mew and Mewtwo are referred to the Gods of the End). But enough about that; I would say in order to figure out how to fix them properly into situations and the plotline in your fanfiction, and good reasons, perhaps reading about and finding good-quality stories that uses legendaries in their fanfictions and analyzing how they work well with the storyline. It can be very difficult handling them, because you have a lot of power and strength to write about, and therefore, may give you reasons to go overboard and causing people to turn away.
Basically, I feel as though that if you want to include legendaries, make sure that you have reasons, explanations, or/and other facts as to why they are present, whether it will be constantly throughout the story, scattered about, or just a one-time ordeal. But, if pulled off well, it can sometimes enhance the plot and draw people in, for they know you can handle them and love to see where you take the legendaries.