If this was for a game, the first two nightmare creatures would be “low level” enemies.. they’re pretty much basic and fleshy. That being said; I have no doubt that they’d be dangerous.
This next guy is a level up with a bony armour plate on his shoulder and upper part of his chest. Maybe I should think of some protagonists as well if this turns into a concept art for games fun side project.. we’ll see.. I’ll keep it fun though.
As always; click it for larger version :)

nice one, bru’!