Not all monsters are treated equal. Some have been introduced to monster manuals edition after edition. And yet...they aren't often seen at the table or adventures. They may show up for one fight, may even frequent as single appearances, but after that and beyond that they are forgotten. Sometimes they are based of myths with much deeper roots than is revealed, myths that give you many options for which to use them beyond the battle. The Libris Monstrum is for those creatures to showcase the reasons you should use them more, to use them in different ways, and to remind you there are more than dragons in Dungeons & Dragons.
Number 1: Naga