Burrow works like Wraithform

[Chronosplit]

Burrow is supposed to dig through walls, unless of course they can't be dug through. For some reason, this isn't the case for me... sort of. Instead whenever I use Burrow and run into a wall that's part of a vault or something, I pass through while losing air as if I'm in Wraithform. Diggable walls work as expected. Also if I'm ever knocked back by an enemy into a wall I end up inside of it. This wasn't a one time thing either, every single time it worked like this.

[Snarvid]

Interesting. I recall that as a Possessor, Wraithform in many bodies frequently worked like Burrow, leaving permanent gaps in the walls. Apparently there's some slippage between the two categories.

[Erenion]

So, from looking at the code, the way Burrow works is as follows:
- it lets you walk through walls
- each time you move (probably not on forced movement, but not sure), if you are in a diggable square after your movement, you dig that square.

Concerning the possessor part, there are some bodies that dig out any tile they move through.
On a quick glance, those are:
- Sandworm Queen
- sandworm tunnelers
- Corrupted Sand Worm
- Briagh
- umber hulks

And yes, knockback can move you into walls if you can pass them. Not just that, random teleports can teleport you into walls as well.
The best part is, that if you enter a level where golden chests can spawn for the first time while able to pass walls, the chests can spawn inside of walls.
(Turns out, when you make an add-on class that can walk through walls with a sustain, you find out a lot of fun things about how that works.)

[Snarvid]

Mmmm, I'm pretty sure it was not one of those forms (which have passive burrow) and I had explicitly used Wraithform. Will see if I can reproduce off a saved game.

e: Yes, did with the Crusher's body (boss forge-giant before High Peak) and his Wraithform functions as Burrow. I have confirmed that the body does not have a passive Burrow ability.

[HousePet]

I seem to recall something about passive burrow getting stuck on in some conditions. Perhaps Possessor is it.

[Snarvid]

I don't know what that means in practice, but you can't just passively bump-burrow a wall as the Crusher, you have to be in Wraithform.

[HousePet]

In practice it means that any tile you move to is changed into floor. It doesn't let you move into a wall, but should something else let you do so, it will turn into a floor.