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These creatures are not from Heroes of Might and Magic 7, but from version 3.58. Of course, they won't be as strong there as they will be here. + Perhaps, for those to whom I assigned the charge attack, I should remove the flying ability, just in case it doesn't work 100%. And all of them are large creatures.
And there are 8th-level creatures there, besides dragons; these are just recolored versions. They look exactly like the 7th-level creatures, but with a different color. Many of them already have immunity to deadly cold, but the cave demon's blade, spirit ability, or crossbowman's shot or charge attack MUST take them down; otherwise, it will be impossible – crystal scales will definitely be unnecessary, and the originals don't even have immunity to damage reduction – I tried to make the abilities as close to the original as possible. In the original, all of them, except for the undead, are taken down by gorgons (these are like cows that have the ability to take down several more creatures after an attack, 5th-level hydra castle).
And in general, there are also some divine creatures and 2 spells and summoning abilities that can take them down.
They should be made in a similar way to the Mystdragon (just recolored the astral dragon), and that's it. An example is in the attachment, as someone has already done.