Wow.
I would say keep the percussion and the staccato brass going while maybe add in some low strings that are sustained?
I love what you have so far, feels like one of those fights where you finally get to do battle with your rival.
In my opinion, by keeping the percussion and brass hits going while adding something on top, will begin the slow climb to a build up...but that depends on where you want the track to go.
Maybe switch up the percussion patterns a bit while adding in other percussion instruments?