This battle map has several phases that change as the fight goes on.
Here's a quick reminder, just in case you wanted to use one of these phased battle maps on Roll20, and not sure how to: you can just go to the map layer, and put the phased maps, from last phase to first, on top of each other. Then when it is time to get to a new phase, you can simply right click the top layer and then click "Send to Back".
If you are a Foundry user, I have Scene Phaser that makes it super easy for you to use phased maps in Foundry!