Arc Raiders once had an Arc called The Cylinder of Pain, so I asked Embark about The Cylinder of Pain, and it turns out The Cylinder of Pain was a proto-Bastion with a big cylinder – of pain

Arc Raiders developer Embark Studios threw out a lot of Arc designs while hashing out the themes, physics, and machine learning of its extraction shooter. The pile of unused Arc designs dwarfs the lineup of machines currently in Arc Raiders, and I got a peek at the cutting room floor during Embark's recent GDC panels, and in a follow-up interview with machine learning research lead Martin Singh-Blom.

At GDC, we heard tales of a circular "piston bot" that used hydraulic or similar pressure to propel itself around the world. The Baron husks found around the game's world were once vaguely Queen-like monsters roaming the fields. Singh-Blom tells me of "something that looks more like an ant, something that looks more like a dog, something that looks more like a ladybug."

"There's been lots and lots of different types of bodies that we've tried that haven't made it," he says. "And without spoiling anything, I hope, in the future, we will revisit many of those and see what new kinds of body shapes we get in the Arc." With advancements in the tech used to build and control Arc, Singh-Blom thinks "at least some of those ideas will certainly be possible to do."

One cut Arc caught my attention. Rather, it caught my attention, grabbed it with both hands, and shook it by the shoulders. Enter: "The Cylinder of Pain." In a short video clip in Singh-Blom's presentation, this thing looked like a grain silo on a mobile platform. I had to know more, so I asked him point blank.

"It was a very early demo," recalls the keeper of the cylinder. "If you look at it carefully, you can see that it's basically the same body shape as a Bastion. I guess in some sense it morphed into the Bastion in the end. It's bigger than a Bastion, probably twice the size of a Bastion. But the idea was, it looks like a water silo or something.

"And on the outside of it, we wanted to have a little procedural puzzle. We thought you'd shoot off an armor plate on the cylinder, and you see a glowing green wire, and then, oh, we have to follow the glowing green wire to get to the weapon system. And then you'd shoot off a few more armor plates, and you get to the energy source for the weapon system, and you could blow that up and take that capability."

Singh-Blom says the idea was to try out "procedural puzzles" that would create "new ways of taking down" the Arc every time. "It sort of worked, but it was so ugly and so early," he says. The machine learning tests worked quite well in the end, but "the procedural thing didn't work out as fun as we had hoped. So that one got scratched." Here lies the Cylinder of Pain, too ahead of its time.

At most, the Cylinder of Pain may end up being a distant ancestor for more complex Arc to come. But one area of Arc engineering, in particular, remains challenging. Singh-Blom says, "We have been very scared of bipeds" – not necessarily humanoid, but two-legged Arc.

"There's a lot of balance issues with, like, how does it get up?" he explains. "I think we could do them now, maybe. We've shown bipeds that work with this kind of system, but it's hard to know how well that works when players start shooting at it and throwing grenades and all these things. How will it attack when it falls over? How do we make it get up? All of these things. So bipeds have been scary for us as a team, and we've been hesitant to try them. Because there's other things we can do before we get to bipeds that would still be really cool, and unlock a lot of capabilities, and that would probably be much easier."

Arc Raiders has a hidden "magic" system: you've never noticed it because you're not supposed to, but it helps Arc do their job