A host, or heavenly host.
The heavenly host would imply all of the angels, or that is "what" they are part of. A gathering of angels is called a "flight of angels". Much like a "murder of crows", "covey of quail", or "clowder of cats".
galaxy
A herd.
A group of nine is called an ennead.
A group of galaxies is called a cluster.
The answer is: a pack ! Isn't that easy?
a group of unicorns is called a unicircle or unicluster
Sheep is always Sheep whether Plural or Singular
A forest, a grove, a wood, a copse, a stand of timber or even a jungle
a litter
The Chillaxes
yes
The angels are commonly divided into nine choirs, beginning with the highest:SeraphimCherubimThronesDominionsVirtuesPowersArchangelsPrincipalitiesAngels