Prestige Class of the Astral Sea suggestion

[Mr.Kraken]

So, in my campaign I'm planning on giving the players a bonus class each, making them gestalt characters. The story is that each of the characters represent one of the main planes of existence in the multiverse (I'm using 4E cosmology). The character that represents the Astral Sea is an Illumian Cleric/Inquisitor. He doesn't have any patron deity, but his beliefs are centered on godhood. To him, the Gods and Powers of the Astral Sea are the rightful rulers of the universe, in opposition to the Archomentals, Demon Princes and other powers.

To him, it doesn't matter if you worship Pelor or Gruumsh, or even Asmodeus. What matters is that your beliefs lie in the Astral Sea - not in the Elemental Chaos. The Astral Sea is basically the equivalent of the Outer Planes, except that the Abyss, Limbo and Gehenna, instead, are part of the Elemental Chaos.

Is there any prestige class that has any fluff suiting the character above?

[Mr.Kraken]

I know it's hard, but let me expand it a little bit. The prestige class should be one that fits the "given by a higher power" kind of fluff, and must be useful (not necessarily for combat). I'd like something neutral, that could represent all of the Astral Sea instead of just good or evil-aligned planes. One of the powers I have in mind to give this character is to transform into aspects of astral creatures - so, he could have the traits of angels, devils, eladrins, archons, yugoloths, and so on. This would be an epic power. The prestige class could be something just as inclusive, but must have the right fluff. Can you help me guys?