"In the valley of mana, twins were born to two great powers, a beautiful sage of unparalleled youthful appearance, and a dragon wizard in human form."
Spoiler (click to show/hide):
I'm pretty sure this wants a semicolon after 'powers':
"In the valley of mana, twins were born to two great powers; a beautiful sage of unparalleled youthful appearance, and a dragon wizard in human form."
Also, I'm not sure 'unparalleled youthful appearance' is the best way to describe it. Perhaps something like 'a sage of unmatched youth and beauty'? Along with it, you may want to reconsider the use of two nouns (dragon wizard) to describe the other person.
"In the valley of mana, twins were born to two great powers; a sage of unmatched youth and beauty, and a dragon in human form."
"In the valley of mana, twins were born to two great powers; a sage of unmatched youth and beauty, and a wizard who was born a dragon but later gained the power to shift to human form."
And finally, 'twins were born to two great powers' sounds a bit weird, considering the first sentence.
"In the valley of mana, a pair of twins had just been born to two proud new parents; a sage of unmatched youth and beauty, and a wizard who was born a dragon but later gained the power to shift to human form."
"However with this joining of such powerful elements, a singularity unfolded that has never been seen before or after."
Spoiler (click to show/hide):
I may understand what you meant, but this is not the right spot for the word 'singularity'. It is a commonly misused word, but I shan't get into details. Along with that, the first segment needs a bit of help, and that the event has never been seen before or after isn't really that strange.
"With the joining of these great forces, however, came a great calamity, a disaster of a previously unimagined scope."
"Nyamene was turned inside out, mountains became deserts, oceans became plains, many of the creatures were fused with other creatures, but worse of all, anything with any human nature was sucked into two dimensions, the twins acting as the fulcrum of this tearing, opposing forces, all of the women were sucked in the dimension with the boy, and all of the men were thrown into the universe with the girl, nothing was as it had been before, the twins were ripped apart into their separate dimensions."
Spoiler (click to show/hide):
Where to begin? The sentence is way too long, segment it. Use a colon to indicate the start of a list. Worst, not worse. Human nature sounds like a strange way to measure something, as it's an arbitrary thing to have. I'm not sure a fulcrum can facilitate tearing. If the opposing forces were tearing, it would be 'these tearing'. How would one perform fellatio on all the women? The sentence is a mess, really.
"Nyamene was turned inside out: mountains became deserts, oceans became plains, and many creatures were fused together with others. Worse yet, all the humans were separated by gender and moved to two other dimensions. All the women ended up in one dimension with the boy, and all the men in another with the girl."
I'm not sure that's good enough, but it's better.
As VintageBass said, some people just like doing this kind of thing. I am willing to help out as well, should you so desire.
I had a nice talk with a friend designer about how to make it better, and he gave me some great ideas on how to change the psychology of the player to actually want to read the text 
