“Now that we are finished leave before you bore me further.”
This line should have a comma after the word ‘finished’.
“Take my portal back to the surface, before I change my mind.”
This line should not have a comma in it. Yes, commas are your friend, but it is unnecessary here.
“Or I could release these waves and make you swim?”
That line should not end with a question mark, as it is not a question.
I realize some of these could be ignored for the sake of a creative direction in the writing, as some people claim there is not a ‘right way’ to write when in a creative setting, such as a video game. If that is the case, please feel free to disregard.