Lovely render, Ohki, and that teeth shader looks awesome, ghostship2. I keep learning new things all the time in this thread.

Here's a little experiment I did in Cycles, going all in (or out?) with the diffuse lighting. Put the character into a room-sized box and aligned a single large area light with the wall on her right and mostly behind her to simulate a window. The ceiling and all walls not visible in the render are white, and the number of diffuse reflections is cranked up to 10. Took a bit less than 8 Minutes on my GeForce RTX 3060 Ti, so I'd say it's not a bad option for environments that are a little too tight to sensibly use an HDRI.

-- I'm not mad at you, just Westphalian.