the book on heroes is ready

Nagas, titans, gremlins, and other similar creatures inhabit the Tower Castle (Tower, in the localization), and not the Stronghold (which we translated as Citadel, and which is inhabited by goblins and orcs). Also, if you are writing about the world of Might and Magic III, I would advise you to first familiarize yourself not only with the third part, but also with Might and Magic VI-VII. And learn the names of the countries.