Firstly, you need to get to the lowest level on the map, where there is a big pyramid in the middle of the room. Around the pyramid are four squares on the ground that glow blue if you stand on them. Stand on all four for about five seconds so they glow brighter and make a cranking noise.
The room should now gain low gravity and you will be able to run on the walls and double jump. There's a variety of symbols on the walls, and you need to wallrun over the smaller blue symbols that disappear when you run over them. If you don't get them all and the zero gravity ends, that's ok as it will randomly start up again the next round and you can finish the remaining symbols in the room.
Once done, in one of the corners further from the dragon, there is a faint wallbuy for the BRM for 1800 points. You will have to double jump and wall run to reach it.
Hope this helped. If anyone is confused let me know to clarify and tell me how to make this guide better before downvoting.