Celestial Evolution Ladder

[Jowgen]

In the lower planes, Fiends turn into bigger meaner Fiends over time according to a pretty well detailed rule-set (especially in Baator). The "Ladder" is pretty well defined.

With Celestials, there is the odd aknowledgement that one kind of Celestial can evolve into another type, but to my knowledge there is no order or list of caveats anywhere. There also isn't anything on how or whether a Celestial can "Fall" in regards to the Law/Chaos axis in a way that lets them either turn into a different equivalent type, or switch lanes when they next "level up".

So this thread is simply to get people's opinions on what they think an appropriate order would be and such. So yeah, what career prospects do you think the common Lantern Archon, Musteval and Coure have?

[Falcon X]

I'm going to have to spend more time in the books for this one, but I believe I remember the gist of it. Albeit, most of my research has been into 2e Planescape, supplemented by 3e books.

Most celestials, when they do gain a new form, do so by divine choice. That is, the deity they are under selects it or offers it to them for whatever reason their portfolio would suggest. Of course, part of this could depend on whether they are "born" a celestial or are a petitioner (dead person from the prime material). I'm thinking petitioners are more likely to change than others.
Also, most celestials have their original bodies for a reason. It's who their spirit is. A Musteval will always be a Musteval (though he may gain more power). A Coure may be chosen to be given an advanced form, though it would be rare.

As for "fallen" celestials, lets look at the few examples we have. Trias the Betrayer (http://villains.wikia.com/wiki/Trias_the_Betrayer) most definitely deserved to fall. However, he did not loose his angelic form, and it's even implied that he may be able to repent and be accepted back by his deity. This leads me to believe that "Fallen" is more of a choice that an archon perpetuates themselves.
Another example is Asmodeus (https://en.wikipedia.org/wiki/Asmodeus_(Dungeons_%26_Dragons)) himself. There are differing accounts, but most agree that he was once an angel that fell. He is a strong analogue to Lucifer.
The general story is that he and his generals were fighting in the war between Law and Chaos (precursor to the Blood War). They fought for so long that Asmodeus and the others started acting like the fiends they were fighting, and because the planes are based on belief, he also began to change physically. Eventually, the Nine Hells were created for Asmodeus and his generals and the Blood War began (still Law vs Chaos).

I haven't read these yet. I'm pressed for time, but here is some further reading, albeit from 4th editions changes:
Codex of Betrayal (Beleth) http://www.wizards.com/files/365_CoB_Beleth.pdf
Dungeon 197: I remember an article on Glasya that might shed some light on Asmodeus

[edit] HERE IT IS. Aright, here is a quote from TSR 2607 "Planes of Law". It is the monster entry for archons. Note that this is a sourcebook from Planescape, which means that it's merely the most commonly held understanding among the people, but that still holds more credibility than most you will find.:
"The petitioners of Mount Celestia, archons have charged themselves with the protection of the plane and all those who are innocent or free of evil within its breathtaking vistas. When a lawful-good mortal dies, his spirit goes to this plane. There his essence is transformed into the body of a lantern archon, the lowest of the celestial hierarchy. However, not all lawful-good spirits change into archons. Some, like dwarves and halflings, become petitioners in the realms of their powers, physically unaltered."
"Although a person can guess an archon's station by appearance, there's an equally simple way to judge it: by which metal accoutrements adorn the archon... the quality of metal shows an archon's virtue within it's station. From lowest to highest, the order is lead, tin, brass, bronze, silver, gold, and platinus. For example, platinum rather than brass accountrements on a warden archon signify its greater obedience to the higher order - it's virtue, if you will - and its greater willingness to serve Law and Good. Once it reaches a still greater stage of goodness, it will be transformed into a sword archon wering lead appointments; it will start the process of advancement all over again in it's new station....
When an archon reaches the next state of goodness, it is not fitted with new metal accountrements; rather, the metal simply transmogrifies into the next state. Because the metal is actually a part of the archon's body and can't be removed, it's unaffected by anything that might change normal metal - including metal0altering spells. The purpose of the metal appointments isn't to confine or hinder or even protect, but to remind the archon of its station so that it might strive to its next level.
All archons of a given station are equal, regardless of whether they have lead or gold accountrements. The especially virtuous (those with precious metals) command just as many lower archons as do the new or less virtuous (those with base metals). There is no difference within the station except that a more virtuous member rises to the next rank (or metal) faster. There's also no jealousy among archons, and there's almost never been a recorded instance of one turning stag on its brethren in order to advance. The one archon who did turn stag decided he was better off in Baator, where Baatezu reward a being for manipulation and scheming; rumor has it he's clawed his way up to gelugon status now. No, on Mount Celestia archons are rewarded for good and virtuous behavior, and that means they're content to stay in their forms until they advance. Nevertheless, it's a joyous day when either body or metal changes."