Angels

"...In the same way, I tell you, there is rejoicing in the presence of the angels of God over one sinner who repents.”

— Luke 15:10

Angels are the exalted Spirits hailing from Mount Celestia.

They are spirits of Good, justice, freedom and other positive virtues. They in large part embody the highest ideal, the closest to pure good.

Creation: Angels are created from the souls of the deceased that have advanced far enough on the path towards the highest ideal. They are then uplifted, either by The Celestial Mountain or by one of his Arch-angels.

Spiritual agents: Angels almost never enter the mortal world. They act within the Spirit World to fight the armies of Hell and redeem the sinners within, but do not seem to act much on the mortal world.
This is not true however: They send messages to priests and holy warriors, answer prayers, grant blessings, most of the time all without needing to manifest in person. They appear in dreams and visions to their subjects to advise them.

Celestial Extremists: Every single angel holds great Power and has spent centuries at the very least on the path of virtue in the heavens. They are mostly unused to the muck of mortal life and are no longer well-suited to it.
The agents of celestia do not often get involved in mortal affairs directly, much preferring to influence things from behind the scenes and keeping their help limited. This is because when they actively interfere themselves, their help is usually not appreciated very much.
Angels are able to see the big picture and pursue the cause of good in a cosmic sense. Thus an angel is more concerned with your eternal soul than your life. What does it matter if your life is cut short by a few decades? It is an insignificant time when compared to the eternity before you. So long as your life was lived properly, you will pass on with few regrets and thus continue on the path towards the highest virtue. This however also means that mortal death is often judged acceptable or even entirely irrelevant by angels, even on a tremendous scale.

When an angel decides to accept a summons from the mortal world it is because some terrible corruption has taken hold that needs to be burned out no matter the cost, to preserve the chance for innocents to be born into a world that allows them to make their own choices. When celestial light manifests to purge the evils on the mortal world, it is a sight to behold.

Fallen Angels

Fallen angels are those who stray from the path. When confronted with the true horror of existence, especially if dealing with this horror for thousands of years, some angels fall to despair and resentment. They abandon the highest ideal, and try to wield their influence more directly. They may try to simply force mortals to be good, might try to stop them from making mistakes, might try to control them, might be too zealous in their eradication of evil, or many other reasons.

If such a thing happens, if an angel truly and unrepentant strays from the path, he falls. He is rejected, gently but firmly by his compatriots, or by his superiors and is banished from Heaven. Most of these fallen angels eventually come to realize their folly and repent, thus painfully finding the path to the highest ideal again and rejoining their brethren in heaven.
On the other hand, some fallen angels do not repent. They may instead become infatuated with themselves and their power and fall fully to evil. These fallen angels often end up in Hades and turn into Demons.

Archangels

Arch-Angels are angels that have been further elevated. They lead legions of lesser angels in pursuit of their duties, according to their disposition and philosophy.
Listed here are the most well-known Arch-Angels and a brief description on them.

Michael - The Sword of God
Michael is the arch angel most dedicated to eradicating Evil. He and those that follow him venture out into both the material- and Spirit World to confront the things that need confronting. He is a patron for righteous warriors and officers of the law.

Gabriel - The protector
Gabriel and his followers are often colloquially referred to as the 'guardian angels'. Their goal is to protect the innocents, or those close enough from the true horrors that lurk in the shadows. The guardian angels also often protect the souls of the dead, as they drift to whatever destinations they go to. Gabriel is often invoked by the common folk in pleas for protection.

Raphael - The Healing Hand
Raphael and his followers focus on restoration. On building up what has been destroyed, collecting what has been scattered, completing what has been left incomplete. He is a patron of all healers and builders.

Uriel - The Light in the Dark
Also sometimes named 'the redeemer', Uriel is a rather secretive Arch-angel. He and his followers venture out to those that have committed grievous sins, but have seen the errors of their ways and seek a way out of whatever hell they find themselves in as a result of their choices. Uriel tries to give these beings the chance to help themselves. The path to redemption is arguably the hardest path of all to walk, and Uriel does not help them along this path. He only helps them to find it or to get to it if they themselves are willing but unable.

Jerahmeel - The guide
Jerahmeel is also sometimes called the Arch-angel of Wisdom. He helps souls on the path to enlightenment, both in their life and afterwards. He and his followers give counsel to those seeking advice on how to live properly and morally, so as to come closer to the highest ideal.

An Avatar of the Arch-Angel Gabriel, the Protector

Appearance:

As Spirits, angels have no set form. However, angels usually take forms that are broadly humanoid, usually incorporating wings, eyes, golden fire or geometric shapes.

Usually, the more powerful the angel in question, the stranger it looks.