I think this should be: "You, the player, decide""You, the player decide what your PC does"
Why "her?" If that's intentional, go for it. I would, however, go with the non-gendered "their.""Imagine yourself in her position"
Strike "that", i.e. "what truths that lie behind the secrets""he decides what truths that lie behind the secrets you uncover."
"And what did really happened to the lost faction, the Sacrifice of Nazareem?""And what did really happen to the lost faction the Sacrifice of Nazareem?"
The rest of the paragraph refers to "missions" plural. Use "missions.""you will have to work together to accomplish the mission in the best way you can."
Unnecessary comma. "in the last decades, through trade""the Zenithians have grown to dominate more and more in the last decades, through trade, hostile expansion and colonization"
I think this should be, "Worship of the Icons" instead."Worshiping the Icons permeates everything in the world of Coriolis."
So this is a bit more complicated, but you're mixing present perfect (have foretold) and past tense (preached) verbs. It should either be one or the other."The omens have foretold it, and the clergy preached it for a long time now"
"These books by...""These book by Alastair Reynolds"
"... deep-space horror and retrofuturistic spaceships fits perfectly...""Alien, by Ridley Scott. Dark, deep-space horror and retrofuturistic spaceships fits perfect with world of Coriolis."
I'm not positive on this one, but I think it should be ".... the Dark between the Stars plays roughly...""In Coriolis, the Dark between the Stars play roughly the role of the Devil in Earth’s Christianity."
"... there is are a bunch of...""but there is a bunch of other tools in the game that will help you build your story."
There shouldn't be a comma before "because.""Treat your dice well, because out there in the darkness"
Neither comma is necessary here."Inside the front cover of the book you will find a map of the Third Horizon, to use when you plan your space travel. Several detailed ship plans are also provided, in Chapter 7."
Either:"Their names were Zenith and Nadir, and their destination the star Aldebaran."
That comma is unnecessary, I believe."The crews lived their lives aboard the ships, through centuries of deep space travel."
Add a comma after "and.""The Zenith continued, alone, and after traversing the empty void, finally reached its destination."
"The portals opened...""The portal opened the way for humanity to travel the stars"
"... considered Zenithian, and the Nomad Federation, Firstcome.""The Syndicate is usually considered Zenithian and the Nomad Federation Firstcome."
... cried "Sacrilege!" and closed..."to which the Order of the Pariah cried “sacrilege!” and closed their home system to all travel."