Café de Nuit

Crosses are also mentioned in the original Monster Manual as a Lawful Good holy symbol that repels vampires, IIRC.

That fits well with Five's idea of a generic or universal symbol.
At least, I think it does.

EDIT

Yep, page 99.

Yeah, that fits in just fine. Though the idea is not really mine. Its an old argument that resurfaces now and again in conversations by horror/folklore buffs...

A universal holy symbol/power only makes sense to me. One that cannot be claimed by an organisation or by a single entity/deity. Its a universal truth, and an umbrella that even the gods of Good serve under and answer to. Individual symbols of power have some of this universal essence in them, but its not "pure". Its somewhat diluted by the restrictions of portfolios (which are fragments of Good), not to mention connectivity issues.

At least, thats what im thinking now. Kinda helps explain why clerics have such a rough go of turning undead in RL too, though a DM could easily carry this over to other settings as well.

The universal symbol of Good, and the understanding and unlocking of its power should be a goal of any mid to high level cleric. The knowledge that their god is but one thread in the tapestry of Light only comes with great wisdom and humble sacrifice (of mortal "trappings")....

Perhaps this truth is intentionally hidden somewhere in the shade of its own brilliance, by the servants of the Southern Cross?

I've always described the simplified Ezran holy symbol as a hilt-up sword for that reason. Associate Ezra with Christian imagery for a closer real-world feel.

Immortal Order

A heretical sect of the Eternal Order

Symbol: “Celtic” cross with a memento mori at the junction
Alignment: Neutral Good
Cleric alignments: LG,NG, CG
Domains: Good, Knowledge, Repose
Favored weapon: Spade

Immortal Order clerics travel the Land doing good works: burying the dead, comforting the dying, and laying to rest the undead. They also act as healers and teachers. Persecution from the EO has all but exterminated the IO within the borders of Darkon but has also encouraged missionaries to go abroad, spreading the cult to new lands.
Immortal Order doctrines agree on many points with the orthodox Eternal Order, but differ on three substantial matters:
1 Those who have been faithful and virtuous in their lives may escape the doom of The Hour of Ascension, escorted by psychopomps into an Ethereal realm of rest, while the wicked and corrupt will be trapped in the darkened Land and damned to undeath.
2 Undead must be laid to rest , not appeased.
3 Azalin is a tyrant , unfit to enjoy the support of the faithful.

IO blood sacrifices are made by self-mortification with a scourge, not the slaughter of animals and certainly not murder of captives.

I might call include " sin-eating" as part of the IO.

Not sure how relevant this is to the discussion, but of note:

The original Ral Partha miniature of Van Richten depicts him holding a cross.

I'd say it's relevant.