So far I've been working at a character concept for a mostly mono-white planeswalker who is a Cleric that puts her efforts to becoming acquainted with religions, faiths, and especially local 'deities'.

My concern is mainly the plane of origin in order to fully take the faith seriously, esp where timelines are concerned (Ula/Cosi/Emeria revealed to be false deities based on the Eldrazi Titans, Avacyn gone mad/dead, etc) that AND the mindset of an individual who can see these figures/religions at face value, through the eyes of a Planeswalker. I want a character who misses the little details that could instigate the nihilistic feelings Xenagos went through.

Any insight into these issues?

Have the character imagine that there are different interpretations of "God" and religion among the planes, focusing on the similarities of many religions across the multiverse. The viewpoint is that "God" set up these differences in order to address unique issues with each plane. Learning each plane's interpretation gives a new view on understanding the nature of "God."

The gods dying/proven false are needed changes to address the changes in culture of the inhabitants of a plane. Ultimately, the worship of Ula/Cosi/Emeria wasn't in vain, but rather pleasing to "God" as the deification of Eldrazi was the means by which "God" allowed the Zendikari to worship "God." However, the previous system is no longer pleasing to "God" and a new, more pleasing system will be set up.

Some deities that aren't provably false and didn't end tragically:

Anyone from Theros (Some are jerks, but Kruphix and sometimes Erebos seem pretty chill)
Anything that apes theros as Amonkhet seems ready to
Most Dominarian Faiths (Otarian Nomad Tradition and reverence of "The Ancestor"; Gaea worship; Serra Worship, the planeswalker had been named after the goddess and later took up the mantle.)
Progenitus
The Kami

Honestly, what you need in this planeswalker is a different view on themselves. They are faithful and humble. Seeing a broad cosmos as a traveler doesn't automatically make one assume that the traveler's being is higher-order than that of a local but empowered divinity. You can take that view, but it's hardly necessary.

Maybe the character could have a more animistic religion, with smaller gods, like Kamigawa, and have spells that actually create and bind lesser gods to things, sorta creating artificial kami even on planes they don't naturally occur, but those kami remain persistent on most planes where they aren't killed, so long as they receive sufficient worship and/or other forms of spiritual and conceptual reinforcement.

Most of their spells would have something along the lines of token generation or the awaken mechanic, and the things created would persist even after they leave the plane. They wouldn't be creating these new spirits from whole-cloth, they'd be creating them _into_ things, like creating the spirit of an object out of that object, creating something resembling a tsukumogami, but without having to have had the object exist on a plane where those form naturally, nor having to have the object exist for 100+ years and be cared about. They don't control the exact form those spirits take because of this, the form is influenced by the medium they are creating them by, and how that thing's inherent influences work. A dagger used to murder people would create a different spirit than one use to defend oneself and others only from active attacks, even if created on the same plane in the same location with the same type of mana. They could also create spirits of the location they are currently in, and such would have different traits depending on the local mana of the plane and that specific location and events that have happened in that location in the past and such, as well as the beliefs of the inhabitants of that plane in regards to place-spirits (if they have any) and that location.

The character could believe that regardless of local magical conditions preventing their formation and manifestations on many planes, that all things have an inner spirit of sorts that merely needs to be properly 'awakened' with the right magical influence.

Another possibility I could see is a divine entity who can reach across planes so long as the faithful one has a proper bond with them. It's clear from Liliana's story that many powerful demons can maintain contracts with planeswalkers across planes, so it holds that it is likely possible for powerful gods to maintain similar holds and granted powers for their faithful, even if that faithful is a planeswalker traveling to different planes. Perhaps they might even desire to create a network of friendly gods through different planes who hold similar philosophies to them to exchange information and use their planeswalker follower to find such gods, and exchange artifacts between the planes that can enable communication between these gods, letting them learn from each-other new ways to perform miracles, methods to help their followers, guidance to help spread their faiths, etc. While artifacts that enable communication across planes seem difficult to create, the lore seems to indicate that they are at least possible to some degree, so someone figuring out a more advanced version of such isn't unfeasible.

It would be easy to have your planeswalker question their god, or challenge it. What about embracing the idea of random acts of kindness (assuming that's part of their faith)?

Well, I hoped to give Ula/Cosi/Emeria, Avacyn, etc some lip-service as entities this planeswalker cleric incldes in her multiplanar pantheon, but am struggling with a starting point and a sort of travel log so that sh doesn't experience a loss of faith due to the relevation that the Zendikari gods are false, or Avacyn's mad/dead, so she'll be absent from Zendikar/Innistrad at the time, but perhaps pick up with Iona/Linvala/Omnath and Sigarda when the tiime comes. It would certainly be dangerous to canon, but a planeswalker cleric unintentionally believing an authentic Emeria or not dead Avacyn into existence on Theros.

While there's supposedly no god/angel worshipped by the Orzhov, I could see her being at home within the Syndicate's church structure.

What information can we extrapolate from sources about the worship of some of these entities?

What difference is there between Emeria & Kamsa, Cosi & Talib, or Ula & Mangeni? Just names? Did the Kor & Merfolk name the same alleged gods differently, come up with them individually, etc? I can tell it's what James Wyatt claims he "made up" about humans in the Zendikar artbook, but what do humans (or vampires, goblins, or elves for that matter) believe about the other 2 if humans went "there was totally an archangel higher in rank than Iona & Linvala, her name is.... what was the name of that one merfolk god?"

Supposely veeeery few know about Avacyn's origins, but apparently angels existed prior, and pre-mending Sorin was going around to every walker who set foot on Innistrad like "this is my neighborhood, have you come to **** it up?" on top of the "Bunny" to Innistrad's Blossom, Bubbles, & Buttercup... is there no record of any of this? Do all the angels keep quiet about their existence prior to Avacyn, no evidence of a 4th archangel or her Flight, and did pre-mending walkers just not put 2 and 2 together about a plane revolving around the structured worship of an archangel who eliminates geists, werewolves, zombies, and vampires when there's a vampire who expends no effort to hide he's a planeswalker vampire who owns the place?

And of course the Orzhov. It's more than likely a cover, but did they USED to pay worship to some deific being (Nephilim perhaps) and it just got lost in translation?

The Orzhov officially worship Orzhova, a form of ancestral worship

Orzhova was originally an angel goddess said to have birthed the world. Literally.

Source is the creative guide sent to the animation studio that did the original Ravnica trailer. They had it up on their site before it went down. It should still be saved somewhere, but I'm on a phone and don't feel like searching.

That's awesome!

Maybe it's the same being as Selesnya's worldsoul.

http://web.archive.org/web/201306031409 ... de24_2.jpg

There we are.
There are more concept pieces as well.
http://web.archive.org/web/201304242230 ... ncept.html

Awesome, does the concept art's removal mean she's no longer canon? Of course, seemingly she never existed at all, as the Syndicate made her up.

Nah, I don't think the removal had any major meta reasons.
That said, there are elements from this that are... pre-canon. Niv's name, for example.

While it's canon is questionable, and probably no longer canon, Serra's religion reached several planes, including Ulgrotha (which she had visited), Dominaria, and Shandalar.

For a similiar example, w/ Ramosian revivalist, it's shown that the way of Ramos had made it to Dominaria, albeit changed from it's initial form.