Well, Sayana did a good job at finding peer reviewers because I'm one!
a beautiful human woman, Eypha, and a river spirit.
River spirit? I didn't know river spirits even existed. This may be something I've overlooked in the lore, but it doesn't sound like something Mizahar would have. Then again, I could be purely mistaken.
Royet heard a young Eypha and her family
It may be the way I'm reading it, but the "a" seems a little weird. I initially thought Eypha was a race or something (before remembering you had mentioned her name before.)
He began to look forward to Eypha's visits, and hearing her speak of her life
The comma is a little redundant here. It flows well without one.
As suddenly as the turn of a fish, one day, Eypha did not return to the river.
Maybe put the "one day" in a different position? Or remove the comma after it.
what children were produced
"What race of children" would make more sense in this context.
the study of heritable traits and how they're passed down from one generation to the next.
I don't know if it is a real problem, but "they're" stuck out a little. I think it would be better put as "they are."
With each generation, the Eypharian family grew prolifically in size as well as power, with many desiring that connection to the family of Eypharian Araka by producing amazing, six armed children.
I think this sentence is too long. I get lost half way through it. Perhaps place a full stop after power, continuing: "Many desired that connection..."
As the number of Eypharians grew, these outcast members of society became the targets of much racism and hatred, finding it difficult to procure housing and good employment, which in turn led to many to become involved in indentured servitude to pay debts.
Another long sentence. I'd cut it at hatred, starting the next sentence, "They found it hard..."
Due to the bone structures, the shoulders and chest of an Eypharian appear to be slightly wider than an average humanoid but are in fact only an average of two to four inches wider.
I don't think these statements should be linked with a "but". You state that they appear slightly wider then give exact measurements. I don't know what you meant when you wrote it, but I would classify slightly as two to four inches. I'd write it as: "slightly wider than an average humanoid; averaging two to four inches."
These glands emerged as a mutation in the Eypharian race in pre-Valterrian times, but there is no evidence it was studied or even noticed at the time.
"No evidence that"?
Very elaborate makeup is widespread on women and men even line their eyes in kohl or use mica dust.
"on women, and even men line"
Those who had been fortunate enough to have been inside huddled, as the rest of the world did, in darkness and impending starvation
I don't find the phrasing of this very fluid - the comma provides a break that separates the sentence too much. Move the parenthesis to the end of the sentence.
For Eypharians, simply reproducing is not enough, every member must uphold and, more importantly, extend the race’s divine glory.
I would exchange the second comma for a colon.
Language
The Eypharian language, Arumenic (Aru= river, Menic= language), has migrated the least from the Ancient tongue due to the continual caretaking of their history by Eypharians. Out of the present day languages it resembles the ancient tongue the most. The sound patterns are similar to the Ancient Tongue but have been over the centuries influenced by common.
You've capitalised Ancient Tongue in three different ways here.
High Arumenic, is spoken by the upper class and any privileged enough to be trained in Semhu.
Remove the comma here.
Names:
What would be nice if a small description of each city could be given. It would help give a little backstory to the names, although would not be at all necessary.
Art:
You mentioned that the body is used in art, but there was no mention of tattooing. While it may not be a common Eypharian practice, it would be nice for this to be stated.
Aging: Do Eypharians age the same as humans? Stating this would be great.
Altogether, a great article, apologies if I've pointed something out that has already been mentioned or only seemed wrong to me. Can't wait to see this fully approved!