Beholder with Class Levels

[willpell]

I've come up with a neat NPC concept for one of the nastier organizations in my gameworld, but am not sure how to make it work mechanically, being a terrible optimizer. The players may well never actually meet this guy (especially given that I'm too busy worldbuilding to actually advance their plot most nights; they've gotten used to the idea of having to wait weeks for a post), but that just means I can relax and not worry about making him too insanely powerful for them to have a fair chance about, and just make him cool and awesome in ways that I'm afraid to do with anyone the players will have to interact with and hopefully not get moiderized by.

So here's the general concept: Beholder cleric of the Patient One polymorphed into a Human who pretends to be a Wizard. And so, the questions: Can a Cleric get Polymorph or does he have to also be a Wizard (probably a Mystic Theurge or some more outre variant thereof)? If he's a cleric, can he get Polymorph through a domain, PRC into it, or somehow access it as a spell-like ability? Or will he have to make do with illusions (the Trickery domain is a given, probably along with knowledge; he's big on "horrible revelations")? Could he even produce an illusion good enough to pass for human while really being a 10-foot-wide eyeball? And what the holy hell is his ECL? The Monster Manual lists a Beholder as CR 13, and CR seems to be roughly between ECL and twice ECL on average, tending higher if you have a lot of special abilities, but there isn't a listed level adjustment so there's no way to get his official ECL...regardless though, just how many class levels do I have to pile on this guy? Since his big evil plan is to awaken the Hecatonchires from the Epic Level Handbook, and it's a plot point that nobody will be able to stop them because my camp doesn't use epic levels (the Hecks are a deliberate rule-break for the sake of doomsday, not meant to actually exist but just be a threat), I'd rather if I could build him as an ECL 20 or less character, but that's tough since Beholders are so uber and he needs at least class 7 levels to get Polymorph anyway. I can conceive of maybe using a Gauth rather than a full Beholder, or even a Spectator, but it'd feel kinda lame. And I really want him to be an actual Beholder, not just a character with a thematic tie to them, although I may eventually end up concluding that's necessary.

I should note that there's no terribly great hurry; I'd like an answer now just to keep in mind, but actually building a character this high-level is far beyond my abilities (and what advice people give me is likely to make my eyes glaze over fairly quickly, though I will make an effort to comprehend it). This is all just speculative work, meant to enable me to lay groundwork by building low-level NPC members of this guy's organization, who will be a factor in the game for years dong deep-cover work long before anyone gets near the guy himself (you can't say I don't work on a grand scale, within the limits of my nonexistent optimization ability).

[docnessuno]

The best option for giving class levels to a beholder is the beholder mage PRC, wich is specifically designed for that (and is also incredibly powerful). That said, the class that won't mesh at all with your concept, since it relyes on eye stalks for casting so i'll put it aside.

An Archivist is probably your best bet. It's a divine spellcaster wich uses a spellbook (a bonus point for mantaining a wizard facade) and is able to grab spells from the list of pretty much any divine caster, as well as domains. Polymorph can be grabbed from the Adept list, and Polymorph Any Object from the Trickery domain.

Southern magician is a feat that allows you to cast your divine spells as arcane (and vice-versa) but it's restricted t humans so it would require some houseruling to work.

Alternative source spell has pretty much the same effect, but requires both arcane and divine casting as a prerequisite.

CR: I would count each class level as a non-associated class level, so the fist 11 class levels would give it +1/2 CR each, while following ones would increase the CR by one. On the other hand i would count each beholder mage level or levels in a class/prc advancing beholder mage casting as associated class level, increasing the CR 1-by-1.
A beholder Archivist 13 would result in a CR 20 ceature.

[mattie_p]

According to this list of domains, polymorph is available via the Alteration and Transformation domains. PAO is available at several other domains at higher levels.

[willpell]

Beholder Mage would be way out of flavor because it requires putting out the central eye. But Archivist sounds perfect. I didn't know Polymorph was an Adept spell and I might settle for just Adept levels, but Archivist is probably a better class mechanically (even though he's not going to need anywhere near the amount of casting it gets given how low-profile he is

I could use some help brainstorming positive Affilitation Score Critieria for his spy ring's members. I have at least a vague idea of the titles and benefits, and the negative criteria wrote themselves (at one point I wrote "kill a beholder: -4" and then realized beholders actively prefer to kill each other, so moved ti down to -1 on the theory that it mildly irks him when a human has the gall to do something that he would have rather done himself), but aside from "levels in Alienist" and the automatic +1/2 character level, nothing sprung to mind as ways to ingratiate yourself to the leader of an organization devoted to exposing every secret in the world, except its guildmaster's identity and purpose. (Given that my world is very meta and self-aware and vaguely postmodern, going Lone Gunmen / Network Zero / etc. on it manages to be both an idealistic plan AND a sinister one, which leads to hilarious opportunities for this guy, one of the setting's VERY nastiest villains, to recruit the willing cooperation of its most goody-two-shoes heroes, as long as they're fairly naive.)

[docnessuno]

Character level: +1/2 Pc's level
5 or more Ranks in Bluff, Disguise, Hide or Move silently: +1
10 or mork ranks in Bluff, Disguise, Hide or Move silently: +2
Can cast Illusion, Divination or Transmutation spells: +1
Can cast Illusion, Divination or Transmutation spells of 3rd level or higher: +2
Worships the Great Mother or the Patient One: +2
Has levels in the Ocular Adept PRC: +1/2 PRC's level
Minor achievement: +1
Major achievement: +2
Slays a beholder: -2
Minor failure: -4
Major failure: Death

3 or lower: No affiliation
4-10: Member of the spy ring, access to "safe houses" in "large towns" or larger settlements.
11-20: +2 competence on Bluff, Disguise, Hide and Move silently checks
21-39: When performign a mission for the ring can borrow a magic item worth up to [Affiliation score]*[Affiliation score]*20 gp
30+: Constant Nondetection, CL = HDs