an ouster angel is?

At one AU, Father Captain de Soya brings up the orbital forest in viewsphere…several thousand of the Ouster-tailored trees, each at least half a kilometer long, move in an elaborate choreography along the plane of the ecliptic–gravity-clustered copses, braided strands, and subtly shifting patterns of trees, always moving, their leaves always turned toward the G-type sun, their roots deep in the vaporous fog of moisture and nutrients provided by the shepherd comets moving among the forest clusters like giant dirty snowballs. Flitting between the branches of these trees and between the trees themselves, Ouster variants are visible–humanoid shapes with silver-reflective skin and micron-thin butterfly wings extending hundreds of meters. These wings catch the sunlight from moment to moment as they open and  blink like brilliant Christmas lights within the green foliage of the orbital forest.