There are two ways to think about angels. You can go with the cute, harmless variety, or the powerful, awe-inspiring, fearsome variety that's interesting to read about. Guess which kind we are?
Hint: we are NOT the kind that look like flying two-year-olds struggling to hold onto their grandfather's musical instrument collection, and we are not the kind you can buy dreamy swirly drawings of, with little notes on the back that say, "The Angel of Solace is attracted by the warm scents of cinnamon and sage."
In other words, we're more in line with the traditional Judeo-Christian angels, and specifically in Seven Archangels: Annihilation, we're borrowing heavily from Christian tradition. I'll explain what's going on.
What are angels? Angels are accepted in the Judeo-Christian tradition as higher-order beings. Unlike humans who have rational spirits, we are rational spirits. We have no bodies and do not have to have them. We were created as angels, all at the same time, and were never human; nor will humans ever become angels. (You and we are separate species.)
But you keep talking about wings and hair color. In the Seven Archangels universe, angelic bodies are fluid to the extent that we can become as solid as we wish. At the far end of the scale, we can completely discorporate and exist only as pure thought. We do this when contemplating God, for example. But in order to have effect on the world, we take a spiritual form. We can change this if we want, but we have a natural affinity to a certain structure. This spiritual form may be more or less solid and more or less visible as we require it to be so. At the far other end of the spectrum, rarely and only with God's permission, we can assume a human form and interact directly with humanity. (And no, you probably wouldn't realize.)
A tidbit about wings: angels with more power tend to have more wings in the Seven Archangels universe, and those wings tend to be of lighter color.
What is the "fall" of the angels? Early on, before the fall of humankind. angels were subjected to the great test, also known as the Winnowing. I won't go into the conditions of the test here, but those angels that passed were admitted into Heaven where we can see God face to Face. Those angels who rebelled were "winnowed" out, and they were cast into Hell after a war headed by the Archangel Michael. The winnowed angels are now referred to as demons.
Please note that in Judaism, the adversary (or "the satan") is just another angel doing his job and is not considered to be evil. He's just been given the unenviable job of putting humanity to the test, kind of like an undercover narcotics cop, and he doesn't necessarily want us to fail the test. In Christianity, Satan is characterized as evil and a liar and a murderer from the beginning and has been cast out of Heaven. This is the characterization we're going with in Seven Archangels.
What are "choirs" of angels? Angels were created in nine orders, or "choirs." Each of the choirs exists in a descending order of power (the way angels are higher-order beings than humans, some angels are higher-order beings than others.) Each of the orders has its own set of defining characteristics, so after a while you'll begin to know that if (for example) Sidriel is a Cherub, then you can expect Sidriel to be fascinated by learning and experimentation and to speak in an overly-specific style and get sidetracked in endless debates over minutiae.
Just for example, "Cherubim" means "fullness of knowledge" and they are the "geeks" of the angelic realm. "Seraphim" means "fiery ones" and they're energized, emotional, and enthusiastic.
The nine choirs used in this book are, in order: Seraphim, Cherubim, Thrones; Dominions, Powers, Virtues; Principalities, Archangels, Angels. You don't need to memorize that. Whenever it's necessary to associate a character trait with a choir, the information will be provided in the text.
For the very-interested, the nine choirs do break down into three triads. The top triad (Seraphim, Cherubim, Thrones) are closest to God and seem most involved in worshipful activities: loving, knowing and contemplating the Most High. The second triad (Dominions, Powers and Virtues) are involved with protection and combat against the enemy forces. And the lowest triad (Principalities, Archangels and Angels) are involved personality with humanity, assisiting us directly in our spiritual journeys as guardians over people, institutions, countries, and systems (like the New York City subway system!)
What is bonding? One of the features of the Seven Archangels universe is that Seraphim and Cherubim, the top two orders of angels, are so extreme that they form spiritual "bonds" with one another. By bonding this way, they balance out one another's extremes, with the Cherubim giving balance and perspective to the impulsive Seraphim, and the Seraphim giving energy and drive to the reclusive and thoughtful Cherubim.
Can angels really die? The traditional understanding of angels is based on a sentence in Luke that states angels cannot die. There's a passage in Ezekiel, however, which makes it seem as if one angel was destroyed by God, and there are several midrashim (Jewish mystical stories not included in the Bible) where angels are destroyed.
What are guardian angels? Guardian angels are, as the name indicates, angels set to guard certain realms, people, things, or circumstances. The psalms refer to angels as being set to guard us in all our ways. In Daniel, we see angels guarding specific countries. In Matthew, Jesus refers to children as having personal guardian angels who see the face of the Father in Heaven. In Acts, when Peter is freed from prison, the Christian community assumes at first that it's his guardian angel that's knocking at the gate and not him. Before Paul is shipwrecked, he sees his guardian angel and is warned that the ship will go aground, but none will be lost. Although some people object to the idea of personal guardian angels for everyone, there's ample Biblical reference to make a case for them.
Seven Archangels does not deal with guardian angels specifically, but other of Jane's stories do.
What are the Archangels of the Presence? The Bible indicates that there are seven archangels who have been chosen to stand immediately in the presence of God. In the Book of Tobit (in the Catholic and Orthodox Bibles but removed from the Protestant Bibles) the archangel Raphael specifically refers to himself as one of the Seven. It's commonly assumed that Gabriel and Michael are also archangels of the presence (Gabriel says to Zacharias that he "stands in the presence of God.") As for the other four, their identities aren't as firmly established, and several mystics (and the Orthodox Church) have taken a crack at their identities. The Seven in Seven Archangels are modified names from a list given in one of the books of Enoch.
What exactly is an archangel? Glad you asked. You noticed above that Archangels were one of the nine choirs. Due to the vagaries of the English language, the same word can mean either "a member of the eighth order of angels" or it can mean "an angel in authority over other angels." To distinguish between the two uses, Seven Archangels capitalizes the name of the choir but leaves in lowercase the authoritative use. (Michael is the only archangel who is also an Archangel.)
Similarly, the word "angel" can mean any member of any of the nine choirs, but an Angel, with a capital A, is specifically from the ninth order. Don't get a headache about this, and don't blame the author--she didn't invent language, and she certainly didn't invent this boondoggle. She blames Satan because she thinks he found it amusing.
