HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

Not quite. All or most of the animations are present in the vid file, but at least the intro doesn't work. Its file is called H3Intro.smk, but the build doesn't play it. Toggling the tweaks didn't help. Another build also doesn't play it. The GOG release runs it without a mod; the vid file has a heavier H3Intro.smk and H3Intro.bik, and there are more animations there, but if you replace the vid file in the mod build with this one, the intro with the Dungeon attack still doesn't play.