Draco's skin turned scaly and his form became less and less like a human's, looking more like a Dragon's. Still, he didn't have enough bloodline energy nor the skill to transform his whole body into that of a Dragon, even in the game, where he had a boost from the Dragon Soul.
He didn't transform into his full Dragonoid form as he had during his moment of climax with Eva. Instead, he resembled a half-human, half-dragonman.
Draco tried his hardest to regain control of his mind, but it seemed impossible. This was a direct result of the urges of his bloodline, so he couldn't resist it easily.
His new body had been re-forged with his bloodline as the base and even his brain had been modified to suit the black mass. It had given him endless benefits, but everything came at a cost.
It was just like how a human could not resist the urge to eat when hungry, no matter how they wanted to keep going on with their fast lest they die.