This hatchling appears to be... dead?

Perhaps not. It seems to be active during the night.

Young dragons are relatively defenseless. They are born with relatively soft scales, which are shed and replaced with harder ones as the hatchling matures. Once a hatchling’s wings grow in, it typically marks the beginning of maturation. At this point they are often capable of hunting on their own and are usually left alone by their mother.

Cursed Bloodblade would have been fiercer than Seth could ever be, unfortunately Seth Bloodblade had frozen him in the stage he is in now. Cursed Bloodblade showed no signs of fear when he was being trained with Emmet Bloodblade, and had swipes quicker than lightening itself. Seth, being the greedy and selfish devil he is, did not want his own "blood" to be stronger than him, so he had frozen him in the stage he is. He will not grow, sadly, but his devious eternal life brings doom upon all.