I haven't actually seen any discussion about these on this sub, so sorry if this is known already.
Outside of the map are what looks like four wooden structures with what appears to be carvings of deer heads on them.
There is one on a cliff out past the graveyard, one down the road from Tyr's foot, one on a cliff overlooking the dry dock, and one at spawn across the lake.
While they do appear on Standard, they only seem to have a single deer head each. On Cursed, they each have different amounts of deer heads, ranging 1–4. What's more is that the number of deer heads randomised between games. From what I can tell, they do not change during the match. With a Gift Card GG, I've checked all four on Cursed round 1 and they definitely have 1–4 each. I checked before exfilling on round 11 Standard, and they all still have 1 each.
The fact they have more heads and randomise per game on Cursed, when they each just have 1 on Standard, means this has to be something. The fact they exist on Standard could just be to throw us off, maybe? I've tried a few things already, but can't seem to find out what to do with them.
I've tried shooting them in order with guns (including with the Mr Peek's ammo clip at the top of the lighthouse and Napalm Burst) and the WW charge shot (with the one by Tyr's foot, my bullets seem to impact a invisible wall, but I can get an impact with the WW).
I've tried shooting them (both the stand and heads) with a combat bow and made the first one ignite (above dry dock, in that game), but it went out quickly, so I think that was just the normal combat bow fire patch. I struggled to hit the second one (which was the one from spawn) and because the first didn't stay lit, I sort of gave up. So, it could still be that. I really thought I was onto something with the bow; it felt like it could've been a nod to DE.
I've also tried shooting them (with a weapon and WW) with Wildfire active (fireball augment), and nothing of note happened. I haven't tried bow + Wildfire, though.
All of that was done post-20. Not ON round 20, so that could be worth trying idk. Given that, assuming this is connected to one, only Grim relics are left, then tier isn't going to matter (though all the stuff I did experimenting were tier III).
I don't have any actual reason to think you need to set them alight, just feels like that's what it is. The order could be some kind of code for something, though I'm not sure what. From what I can tell, there doesn't appear to be spot in the map where all four are in line of sight (the one near Tyr's foot one is the only one visible from Tyr's head, and can't been seen from atop the lighthouse). All I know is that in Cursed, these structures have a different amount of deer heads to each other, randomised each game (as opposed to each having one in Standard).