When sea-serpent rises, when wild siren calls,This first line here is odd? I think maybe you should change it to, "When sea-serpents rise, when the wild siren calls" otherwise it sounds kind off weird?
We've only to write, and invent what befalls.
To write is our purpose. [make this a comma] Creation our theme.
A young writer's passion- [you can make this an EM-dash by hitting ALT+0151. it looks like this: — ] A young writer's dream.
To stop writing stories, consider the cost!
A whole other kingdom, forgotten and lost!