What monsters are the most fun / most effective to advance? I know for the most part that advancing monsters sucks, cause they're not really getting anything new, just a buff to some stats, that don't even measure up to level. I know some monsters in later Monster Manuals got extra stuff for advancing them. And of course loads of Monster Manuals had advanced versions of the monster right there to use. But what ones are the coolest or underrated monsters to advance?