Chests in walls.

[LordBlade]

So an issue I'm seeing with the new DLC map is that sometimes "bosses" spawn inside walls and other inaccessible areas, and can be killed there, making the chest unreachable.

[Cahos Rahne Veloza]

Mad Groove Arcana mate.

[Rotting Pastry]

This can happen in lots of maps. Chests will push themselves out if a boss dies in a wall. So if it's sitting somewhere, there is probably a way there.

[LOSERCITY RESIDENT]

you can use eskizzibur's 5th upgrade to pass through walls