This was a fun waylay but your opening scene is actually a good teaching moment to showcase how redundancy can happen in writing: "sands of the ground beneath him" and "high walls surrounding him" and "aliens cheering/in a language he couldn't understand" and "inside the cage, slamming against the cage walls" and "tall, lean muscular, towering, 7 foot tall" - There's tons of these lines everywhere. Don't be afraid to use the short or incomplete descriptions of things and let the reader finish painting the picture with the rest of the text.
I really like the idea of a monster of a man calling an enemy a monster, that sentence alone makes sure that I know whatever it is, its big.