The Hidden Folk

Carried aloft, half conscious (see here), Theor sees:

ammonia smoke;
winged shadows, weaving and vanishing -

- and hears:

flutings and chimings from the flying creatures;
booming wind;
the thrumming of the cords binding him to his improvised parachute.

Borne down by the wind out of the smoke, he sees:

the sky as "...an immense black vault..." (p. 96);
the sun, for the first time in his life;
red clouds below him;
umbras and penumbras;
a circular rainbow caused by ice crystals;
mountains;
lilla and pirell-brown forests;
a volcano;
around him, the flying "Hidden Folk" -

- three feet high;
slender;
fluke-tailed;
broad membranous wings;
two legs with grasping toes;
sharp noses;
curving necks;
small eyes;
arms with hands and opposable thumbs;
some carrying ropes or harpoons;
lacking throat pouches or gills;
calling from their mouths;
breathing like human beings.

Another race of Flying Men.