Church of the Highmost

Church of the Highmost is not only the numerically biggest organized religion within the multiverse. It is also one of its greatest military superpowers, and a de facto government of a Throne World of Elysium. It is hard to find a Vassal World without at least a single country with a majority of its population following the Church's creed - especially if one counts the remaining Christian churches as autonomous parts of it (although in all honesty, they are more like protectorates). It is also the only notable religious organization following monotheistic doctrine - a great achievement in a multiverse where divinity is so common.
On the surface, the Church is concerned mostly with proselytism, charity efforts and preaching - plus of course highly militant self-defense. This is all true, naturally - however it is far from being the full truth. The Church is playing a long-game for dominance over the multiverse, fully aware that the days of the Dominion are counted. When Terra will stop being a sleeping giant that everyone's afraid of waking up, there will be a war. One not on the same scale as the Great Multiversal War, but with way more participants. Church of the Highmost is preparing fo that day, building up its forces throughout the Multiverse.
What's more, the leadership of the Church tends to be seen as always helpful straightforward and honest - after al, they are celestials, so they can't be expected to scheme, right? Unfortunately, that, too, is patently false...

Structure

Majority of the Church of the Highmost is virtually indistinguishable from the Catholic Church. You have priests with their parishes, you have monks in their monasteries and nuns in their covens - plus knights for the holy orders. Then you have bishops overseeing parts of the world, archbishops controlling larger parts of the world, and finally a handful of cardinals (typically current or retired bishops and archbishops), who are tasked with electing the head of the Church in that world, the supreme pontiff (local equivalent of the popes).
Above the level of a world there is the Church's leadership - namely the Theological Council, composed of representatives of every heterodoxical school of thought within the Church as a whole (which does include the representatives of the 'vassalized' religions, for example the surviving and relatively unaltered remnants of terran Christianity). That's what the multiverse believes to be the ruling power of the Church.
Only a very limited group of people knows that within the Theological Council there is another, much smaller group. The executive power to the Theological Council's legislative power. It is the Eschatological Council - a group of six incredibly powerful and influential people dedicated to the applied eschatology - the long game to see the multiverse end according to the Highmost's will, and not a second earlier. Until Highmost announces his decision - an event most unlikely - the Eschatological Council is busy ensuing that no world or multiverse ending threats will come to pass.

Cosmological Views

The Church of the Highmost believes that the world was created by the Highmost - for reasons mostly unknown. Unlike Christianity of old, the Church of the Highmost has put a much bigger accent in its theology on how incomprehensible a true Creator God has to be. The most popular theory is that Highmost, in an essence, is an all-loving deity - and without something to love, His own existence would simply be lonely. However there at least several different ideas on the issue.
A deviation from the standard theology is that according to the Church, Highmost's activity was limited to the very moment of Creation - once the universe was established, and matter thrown away by the Big Bang was 'scheduled' to merge into the planets (where life could start), the Highmost has mostly took a backseat. Allowing its servants - angels in their numberless legions - to shape the live into numerous forms through subtle guidance over the natural processes.
Some theologians have come so far as to suggest that the Dark Lords might have been angelic creators of some distincly inhuman species that have somehow 'fallen', driving them insane - still with their power of creation and control over what they already created. The Church's general stance on that is that it is heterodoxical, but not part of the official dogma.

Tenets of Faith

1. I am the Lord thy God, thou shalt not have any strange gods before Me.
2. Thou shalt not take the name of the Lord thy God in vain.
3. Remember to keep holy the Sabbath day.
4. Honor thy father and mother.
5. Thou shalt not murder.
6. Thou shalt not commit adultery.
7. Thou shalt not steal.
8. Thou shalt not bear false witness against thy neighbor.
9. Thou shalt not covet thy neighbor’s wife.
10. Thou shalt not covet thy neighbor’s goods.

Ethics

The ethics of the Church are largely indistinguishable from the Christian ones. You should be kind to others, humble, patient, diligent and charitable. Taking responsibility for your own decisions is seen as necessity. Wrath and impatience, envy, pride and greed should be avoided at all cost, as they are faults of the character - and a major ones. As a whole, you can expect the Church to be much more interested in your personal life and daily behaviour than most of the other religions.
The Church tends to be among the few remaining groups at this point who can be expected to complain about the way your country is organized. In a way, the Church of the Highmost is probably the last group out there that truly believes in the concept of human rights (at least in its own version of those) - and militantly so. It can - and probably will - violently oppose slavery, any forms of genocide or ethnic cleansings, and various other form of systematic oppression that nobody in the Dominion sees as in any way unnatural at this point. Often against their own long-term interest, merely on the basis of a moral outrage.
Among things that irritate the Church (but do not trigger violent response) you can expect things such as abortion (although celestials might get violent if it happens near them), various unexpected forms of marriage (for example polygamy), and worship of the High Archonts (whom the Church absolutely refuses to tolerate in any degree or shape, although prefers voluntary conversion to summary execution.

Granted Divine Powers

There are six main branches (called Aspects) of the holy magic dedicated to the Highmost. They are (all) characterized by primarily light themes and tendency to cause more damage to people who are evil (especially when they are in act of committing some major sin), while their positive effects scale accordingly to how much of a decent person you are - unfortunately using them to gauge someone's character is impossible, as they tend to not work when not used 'for real'.
As a rule, these magic 'schools' are incredibly powerful and cost-efficient. However each of them has some major downside - if not a curse - that has to be taken into an account by their practitioners, and can be sometimes exploited by their enemies as a weakness.
The Aspect of the Knight is all about willpower and determination - and readiness to stand up for those weaker than you. It's mostly concerned with defense in the melee, allowing its practitioners to soak up sometimes ungodly amount of damages - one of the strongest spells of this aspect actually makes you invulnerable to all damages for a set period of time. The problem is that you will still feel the pain that you would normally feel - and you will either receive wounds if the pain will make you flinch if your oath to defend those that cannot defend themselves - and lose all your magic forever (or until sufficient, heartfelt penance) if you flee.
The Aspect of the Crusader is about the willingness to fight against evil - not defend against it, but to actuall march out to stop it before it endangers others. It's the offensive equivalent of the Aspect of the Knight, offering much more mobility and ability to cause terrible amount of damages against those who are evil. The side-effect is that you can expect the magic to not work - or even rebound to you - if your judgment was clouded and you attacked those who were innocent. Sufficiently nasty cases of the rebound might be disfiguring or even lethal.
The Aspect of the Mage is focused on studying and controlling environment. You can expect 'blessed' variants of many elemental magic spells, allowing you to rain death from afar. Magic of this Aspect is often underestimated, typically to lethal result. On the other hand, you can expect this magic to be 'wild' and uncontrollable - your own holy fireball WILL lash out at you if your character isn't good enough to earn its acceptance.
The Aspect of the Martyr is about dedicating yourself to others. This is an aspect composed mostly of support magic - the practitioners of the Martyr magic can heal you, defend you from harm or even transfer all the damages your are about to receive to the caster. One of the most potent spells of this schools allows you to actually resurrect someone (provided that they were Church adherents, or died relatively early - and in both cases they had to be someone you personally knew and love), although usage of this spell is paid for with your own life. The massive weakness of this aspect is that from the moment you choose it, you can no longer be healed or supporte with it - including your own magic, or that of the others.
The Aspect of the Inquisitor is mostly concerned with the truth. Its practitioners are capable of detecting all forms of lies, can easily detect invisible or hidden, will sense an evil intent at a large distance, and in some cases are capabe of foreseeing disasters or other tragedies that will soon happen. Unfortunately, there is a curse following this blessing. You cannot forget the truths uncovered with your magic. Many of the older practitioners of this school are reduced to gibbering wrecks by what they seen and felt - and the most stalwart of hearts might allow you to remember that there is still good out there.
The Aspect of the Disciple is the highest and most powerful of all the aspects. Learning even the slightest part of it makes you into increasingly powerful reality warper, capable of downright ordering Reality around - a senior user of this school can simply order the spell or an attack (or even the attacker) to cease to be, conjure their own attacks by telling them to be, alter the results of the recent events - or knowing the future ones. It also means learning and understanding the universe to the level impossible to fully describe to others. Unfortunately, the more powerful in this aspect you grow, the weaker your grip on your own existence. The eventual results is turning into something that no longer resembles yourself - and eventually ascending into something existing elsewhere.