Write on the brick wall with the quill "goodbye my friend," then go upstairs
It seems silly since you're sure he wont be able to read this.
Be sure to thank your master for your new voice and wings. Stay on good terms with him! You don't know how angry he might be at you for snooping around.
Dr. Agony: "Good morning, how are you?"
Dragon: "Um, thanks for the wings and my voice, master."
Dr. Agony: "Don't mention it, I felt that a week was all it took for when you were ready." "Listen, I'll be heading out again soon and would like you to tag along. I've already prepared an invisibility potion so we would leave the gates more easily."
Dragon: "Oh, I guess that sounds fun."
What questions are to be asked?