Ardeadai liked the feeling.
While the innards of Ardeadai where around the same temperature as that of a neutron star, he could still feel the draconic heat. It was good, very quite good, a feeling he assumed would give give him dragon blood. When the a quarter of the chalice was emptied, Stygia kissed him again.
Ardeadai smiled, feeling the power of the blood, and what it would give him... In less time to even as much as notice, Ardeadai had transformed... and it was beautiful. His body was wholly black, each individual scale being many times sharper than any mortal weapon, they where made of a material that made steel like like jelly, without losing the agility needed. His draconic eyes aflame, shone a light out of them, on his back, along his spine, where especially sharp death-weapons...
And Ardeadai was loving it. His teeth could snap open diamonds, his ears could nearly hear a feather drop on mars, his wings, OH, his wings! They where magnificently pitch-black, spikes everywhere, and it was perfect. His long, prosperous tail had a steady stream of hellfire coming from it, along with 4 identical spikes evenly distanced on it, all facing behind him; at the troubles he once held.
He was magnificent. While, from a distance, he may look like any normal dragon and even near-identical with Stygia's dragon-form, from up close he'd put even the dragon gods, many of which he had slain, to shame. On each of his four feet where four brilliant claws, a reminder to not anger him.
He was pleased with this form, and surely Stygia would be too. He made a steady stream of dark blue hellfire, half-melting the stone of the roof, showing off his new power. It was absolutely brilliant. He was quite large, being taller than the castle if he stood up on his hind legs.
He looked down at the now-tiny Stygia. "This gift, it's wonderful. Now, I wonder if you'd like mine."