Creatures do not receive fall damage
I've been hurling levitation spells at a pissed-off cagouthi for a while; it did rise to execute its redemption on me and did also promptly fall to its doom as the levitation spell expired. However, there seems to be a problem with the "doom" part.
Just for the sake of experiment, I've pissed off some guards and made them airborne. They did indeed fall to their doom, and the doom did come after a couple of flights.
This was not the case with the dreaded cagouthi. The beast endures. The beast flies. The beast falls in an utterly hilarious way. The beast endures still.
Either the beast has inborn slowfall or the All-Maker hasn't implemented fall damage for creatures yet. See for yourself in the attached game save right above the humongous beast.
(RM-2201 from redmine: created on 2014-12-09 by Sergey "Shnatsel" Davidoff, , closed on 2014-12-13 by scrawl .)