BURN 4 FLAGS
1: As soon as you enter the gun battery to get to the bunker, you can find this on the wall behind the large gun.
2: Once you get to the roof of the building, before jumping down look to the northeast side and the banner will be on the wall there.
3: In the main room where you get attacked by a large group, look on the wall above where you enter, and you can find it high up. To light it, you will need to nail it with a fire arrow.
4: At the Endurance overlook camp site, look up the crane to the right of the building and you will see it way up high. Shoot a fire arrow at it to burn it