Time was, angels and demons were all lumped into the same bucket. They had different characteristics, depending on the specific entity in question, which is where it gets splintered out into “good”, “evil”, and “fallen”.
Many angel names will be identified as good/light in one culture/religion while the same names are attributed to bad/dark in another. Then, of course, Gnosticism flips the whole pantheon of angels on its head. It’s all relative.
For the most part, our history of angels goes back to the Greek daimon. This is ignoring the Islamic retcon that sends angels into Babylon, long after the fact.
Some interesting stuff regarding the daimon:
Daimons, in ancient Greece, were considered divine powers, fates, guardian spirits, or angels, who gave guidance and protection.
"Everything daemonic is between divine and mortal"
Diotima goes on to describe daimons as;
"Interpreting and transporting human things to the gods and divine things to men; entreaties and sacrifices from below, and ordinances and requitals from above…"
In other words, daimons are demi-Gods, with divine power, existing between heaven and earth, playing the role of intermediaries, between humans and gods.
Of what order is this daimon, which manifested itself to Socrates in childhood but was also heard by Apollonius of Tyana only after he had begun to put into practice the Hermetic principles? “They are intermediate powers of a divine order. They fashion dreams, inspire soothsayers,” says Apuleius. “They are inferior immortals, called gods of the second rank, placed between earth and heaven,” says Maximus of Tyre. Plato thinks that a kind of spirit, which is separate from us, receives man at his birth, and follows him in life and after death. He calls it “the daimon which has received us as its portionment.” The ancient idea of the daimon seems, therefore, to be analogous to the guardian angel of Christians.
The Greeks called that distant voice within us, that higher source of inspiration and enlightenment, a person’s daimon.
As Christianity began to take over Greek and Roman traditions, Christian scholars produced several new interpretations for Daemons.
The most famous re-make is the “demon.” Christian demons are based on Roman stories about kakodaimons, the evil spirits who persecute men with bad luck and sinful impulses.
Another re-make is the “guardian angel.” Daemons, who are described as semi-divine beings who are created when good men die, are very similar to Christianity’s angels. The common Roman belief that Daemons watch over us inspired the Christian belief in guardian angels, who do the same.
Socrates
Socrates, the father of Greek philosophy, was famous for claiming that he was born with a personal Daemon, who the gods had given to him as a gift. Socrates described his Daemon as an “internal oracle,” meaning that the spirit was part of himself, instead of a separate being. The oracle spoke out whenever Socrates was about to behave wrongly, but when he was correct, it said nothing. In this way, Socrates’ Daemon was a lot like today’s “conscience.”
Plato
Socrates’ most famous student, Plato, put a slightly new twist on the Daemon. Plato claimed that a Daemon was assigned to every man, at the time of his birth, so that he would always have a noble spirit to guide and guard him through life. Unlike Socrates, Plato specified these were external beings. They were attached to men, but they didn’t belong to men. In this way, Plato’s Daemon was a lot like today’s “guardian angel.”
At the end of the day, angels and demons come from the same root origin. And I don’t think it’s much of a stretch to identify them as aspects of higher consciousness. Even the old-timey philosophers kind of acknowledge that.