there are three types:
proclaimers:executioners that resemble angels, these get their name because they proclaim the destruction of the galaxy.
enforcers:executioners that resemble large dragonesque winged demons, these get their name because they enforce the will of the creator, milky way's destruction.
convictors:executioners with a strange setup, these are smaller than enforcers, small enough to be humanoid, they wear a black cloak that covers their whole body except for one eye, which glows red (kinda like a robot eye in appearance) with angel wings that look like they are in shadow (not EXACTLY black) these are like enforcers, but compressed.
(SPOILER) the reason they look like demons & angels is because they WERE sent by the creator, so their appearance understandably resembles the apocalypse.