Aleksei shakes his head.
"I think you misunderstand, Ms. Ithil. We do not hunt dragons for their bodies to make these changes. Even with the hands and the will, there would not be enough. But in every scale and drop of blood the whole essence of the dragon is replicated." He moves on past that recovery room.

"Not only with dragons, but most creatures are not suitable. Trolls' blood is already too diluted and similar to humans' to have much effect, and hydra cells grow out of control and consume the recipient. For instance. We've had luck with certain trees, though, and new investigations are undertaken where we can."

The next place the pass is a surgical area, concealed behind many doors as part of keeping it clean. Little to glimpse, and it doesn't seem in use right now.
"True, the very first of our nephilim (that was well before I started working with her, of course) was made how you imagine, but it's hardly the standard way for these things."

And they come to a little rest area outside the doors to a stairway. "I'll ask you leave any weapons, cameras, active magical items, etc. up here..."