The problem I have with that for the greater mythic monsters (dragons and anyone else really, really badass) is that most of them were able to take down many of the greatest heros, until the protagonist figured out how to attack their weak spot. And in many cases, the protagonist was more of a commoner than any great hero type. But the players, having heard the same stories you have, will make a beeline for the weak spots, ruining the mythic feel of the whole story.
And as for the more "generic" mythical monsters, well, the only reason that orcs and trolls are so banal now is because we're used to them. I'm sure that whatever monster you make, unless it's so super powered that they don't stand a chance against it. In which case you're just railroading; it's one thing to have the party encounter a monster that can eat them for lunch, it's another to have them see something new and have it wipe the floor with them. Making a monster far more powerful than the PC's just so it'll scare them is very poor form, and doesn't really inspire any player emotion.
So if one of those mythic creations sparks your imagination, more power to you, but at the same time, there's a lot to be said for taking a pre-existing creature and just changing the "skin", maybe making a tweak here or there, than totally reinventing the wheel just because you want your players to be in the dark.
). Palladium could hardly sue anyone for using them in a game, any more than they could sue people for using vampires or werewolves.
