When you must fight

[Warmaster Horus]

Sure, rewrite.

For a story of this size there are quite a lot mistakes in grammar.

Yep, and the main one I find is that you can't see immediately whether the sentence is spoken or thought.

Example:

He was Aristarchus of Sparta, the Greek leader.Son of Isidoros the Lucky, he learned how to fight against Romans.He was 'the Roman Nightmare'.
Yes, little boy.We know whats going on.Please calm down, go home and dont return to this place unless we tell you, understand?

If I understood correctly, the italic part is a dialogue and the first part isn't. But here, nothing shows it.
Sorry if this insults you.