I AM UNCERTAIN???? (Yes this is a repost to make it its own post rather than a repost, looked messy)
I'll try and break down my reasons for these suggested domains (which are not required to follow for these specific deities, do whatever you think feels right .w.)
The asterisk (*) means it is partnered content, and is not considered "official" (I just wanted more options listed)
Known to be benevolent and fair, seeing justice throughout the world (speculated to at times be a bit strange), Irene is connected to a lot of things. Rebirth, restoration, light, various stuff.
Why the Light Domain?Well... In the official D&D cleric domain subclass, it is described to promote the ideals of rebirth and renewal, truth, vigilance, and beauty. Aphmau is, while technically Irene herself, is also considered to be a type of reincarnation?
On top of that, Irene gave parts of her god-like abilities in the form of relics (I think????) to the Divine Warriors, granting them immortality. However, instead of being incapable of dying, they're instead put into a cycle of rebirth, which is still a form of immortality in some cases.
On top of that, Irene is often associated with the light. In Diaries Rebirth, Aphmau's markings glow with light whenever using her powers, so it felt like a safe bet to associate her with this suggested domain.
Why the Life Domain?Similar reason to the one above. Deities of life often promote vitality and health through healing the sick and wounded, caring for those in need, something Irene is known to do.
Why the Nature Domain?In Diaries Rebirth, Aphmau is able to heal the land with her divine magic. On top of that, Irene is also known to not just heal people, but also heal crops and nature in order to help others, so it felt fitting.
Why the Peace Domain?
The peace domain is a very underused domain in D&D, but despite that, gods of peace inspire people of all sorts to resolve conflict and to stand up against those forces that try to prevent peace from flourishing. This felt like something that'd fit Irene, due to what she's often associated with.
Enki is known to have a thirst for knowledge, especially regarding the arcane. He was one of the easier ones to find connections to.
Why the Arcana Domain?One of the easier ones to explain. He's skilled with magic, and knows how to create magical items out of thin air. Gods of the Arcana domain know the secrets and potential of magic intimately. For some of these gods, magical knowledge is a great responsibility that comes with a special understanding of the nature of reality.
For these reasons, this domain felt fitting for Enki.
Why the Knowledge Domain?Gods of the Knowledge Domain value learning and understanding above all, something that Enki is quite passionate about. He created a massive library to preserve his knowledge and records on the world, and even wrote about each individual Divine Warrior, albeit limited.
Like the Arcana Domain, this one felt self-explanatory
Why the Moon Domain?
The Moon Domain is a subclass primarily from the Tal'Dorei Reborn book from Critical Role. It's stated that Moon Clerics are often depicted as guides, and within Gal'ruk, they have the saying "May Enki be with you", which is akin to "may he guide you" or something similar.
Shad wasn't always the angry, heartless Shadow Lord we know him in the series. This anger mainly stems from his distraught when Irene turns their daughter into a relic, which seems to indicate he is, in a way, a family man.
Why the Blood Domain?The Blood Domain is not part of the official 5e subclasses, but instead comes from the Tal'Dorei Reborn book from Critical Role. Blood Clerics can stem from two paths: Selfishness and Selflessness.
This domain also holds themes in regards to the connection between soul and body, which felt appropriate for what is known about Shadow Knights. It is about the power of sacrifice, the balance between life and death. It's likely Shad uses this domain for more selfish, and more malevolent reasons compared to most.
Why the Death Domain?A fun fact about the Death Domain, that I learned, is that it was originally created for DMs to create a "villainous" cleric, alongside the Oathbreaker Paladin. However, it's mostly evolved into something more.
The Death Domain is concerned with the forces that cause death, as well as the negative energy that gives rise to undead creatures. Because Shadow Knights are labeled as "Undead" within the MCD universe (which will be different for "awakened" Shadow Knights), especially since someone must die and hold a strong sense of vengeance to get Shad's attention, this domain felt suitable.
Why the War Domain?Gods of war watch over warriors and reward them for their great deeds. Some might be good, some bad, others neutral. The reason why I thought this domain would be suitable was because of Shad's militaristic nature we know him for as the Shadow Lord.
Shadow Knights also, for the most part, always stem from a militaristic background for a more "natural" selection, known to be guards under the rule of their respective lords. Because Shad is forming a military of vengeful souls of knighthood, it felt safe to say he would hold influence within the War Domain of clerics.
Esmund is one of Irene's loyal warriors, her shield, and was a major point of conflict between Irene and Shad, as he held feelings for the woman he protected.
While not much is known about him on a personality level, it's clear he's protective, loyal, and self-sacrificial (to a point).
Why the Blood Domain?Although the Blood Domain can be viewed as an "evil" domain, it's far from it, as every domain can be good and evil. The reason behind the decision to grant him access to the Blood Domain (from Tal'Dorei Reborn) was because he appears to be the kind to sacrifice himself to protect others he cares about.
Even though this isn't a very strong reason, it felt suitable for him in some regard.
Why the Light Domain?Even though it's not much, I feel like he'd hold some influence over this domain because of his connection to Irene, or his stance on being her loyal protector.
There's not a lot of "light" symbolism with him outside of his hair and shield, but considering he's an ancestor of Garroth, and seems to hold up a desire of truth and vigilance (in some manner), this domain felt suitable in some regard.
Why the Order Domain?This domain represents discipline, as well as devotion to a type of law, an institution, or a philosophy. In his case, that would be his devotion to Lady Irene.
Esmund is a knight, seemingly more so compared to the other Divine Warriors. Because of this, the Order Domain felt suitable in some regard (yes, this is being repeated).
Why the War Domain?Although Shad may be a god of war in a malevolent sense, I feel as though Esmund would be the "light" version of this domain, but isn't the only one who would be associated with it.
Clerics of the War domain can include champions of honor and chivalry, something that seems to be what Esmund symbolizes in some manner.
While not much is known about Menphia directly, we do know that she is mostly renown within the Tu'la region, and isn't recognized by many within Ru'aun.
Because of the lack of knowledge known of Menphia, there will be some creative interpretations (as there will be for nearly all of these characters).
Why the Forge Domain?Although not much tells us about what Menphia's personality and background is like, we do know that the Tu'la region is more technologically advanced compared to Gal'ruk and Ru'aun, which are more magic-focused.
The Forge domain focuses on what it suggests: a forge. Essentially a blacksmith's path in religion. The domain practices patience and hard work, and that your patience will be rewarded once something is created.
Although this domain doesn't specify what it connects to the most outside of forging, this option felt somewhat suitable to what Menphia might be associated to in some manner.
Why the Light Domain?Even though Esmund and Irene have some influence within this domain, the reason behind this decision is different from theirs. While she may be a Divine Warrior of Irene, my decision for choosing this is its association with fire and sunlight.
As a follow up on the Forge Domain, fire is necessary to make things with a forge, hence its connection. On top of that, the Tu'la region, mostly in regards to Meif'was, seems to have a type of connection or sense of comfort from the sun.
Although not much is known about Menphia, this domain felt suitable for her in some regard.
Why the War Domain?Outside of being a Divine Warrior, the Tu'la region is associated with not only monarchy, but with war as well. It is known to be militaristic and powerful when it comes to technology.
While only vague, it felt somewhat suitable for her in some regard.
Out of the members of the Divine Warriors, he is one of the few that seems to have the least amount of knowledge known for his personality and behavior.
From what I could find, there's not much in regards to the reasoning behind his title, nor his influence within the history of the Divine Warriors.
Since his title is very vague, much like Menphia's, there will be some creative interpretation.
Why the Grave Domain?This one is an interesting take... Gods of the grave watch over the line between life and death. Followers of this domain also seek to put wandering spirits to rest, destroy the undead, and ease the suffering of the dying.
Deciding to stick with a "Wandering" theme, this domain felt suitable due to its relation to aiding those who wander, such as spirits and undead, hoping to ease other's suffering.
Why the Tempest Domain?This domain is associated with weather, while also being connected to the sea and elements. Many followers of this path may be seafaring folks, and travelers, those who hold courage.
While a good number of gods of this domain are associated with violence and physical strength, it doesn't have to always be the case. This felt suitable in some regard because of its association with travelers (mainly with seafarers).
Why the Twilight Domain?This domain is, functionally, considered a "broken" subclass, as it provides a ridiculous amount of dark vision at level one (in the 2014 edition).
As stated on its page: "Clerics who serve these deities bring comfort to those who seek rest and protect them by venturing into the encroaching darkness to ensure that the dark is a comfort, not a terror."
While not much is known about Kul'zak, this domain felt like something he'd have a connection with. He, along with Menphia were not known to harbor any feelings towards Irene like the other members of the Divine Warriors did, and provided aid when it came to vanquishing Shad.
This gives me the feeling that he's somewhat of a protector, a source of respite for those growing weary from their travels.
Not a lot of these are very strong points, I was just trying to go off what I could find on the Wiki and could come up with ideas that could suit each one.
Of course, deities are not limited to only being followers of clerics, anyone can be religious. Clerics just happen to be followers that devote themselves to the divine and happen to be recognized and granted abilities associated with their respective domain.
You can be a traveling bard who follows the path of Kul'zak, or a fighter who follows the path of Esmund, etc.
And if someone was to play a cleric, I would say that you don't have to limit yourself to these suggested domains to be a follower of one specific deity. That would be very restrictive, and everyone has their own general idea on what domain best fits who.
Anyways, uh...yeah, this is what I got. I'm open to feedback and suggestions! (I will be making a guide on how to make custom deities within this as well, as it was stated that Irene and Shad were blessed by EXISTING GODS that seem to have little to no influence over the main story, so who's to say there can't be more outside of the Divine Warriors? [insert shrug emoji]
