Obsidian Wall

The lava wall set lines the deepest part of the cavern layer, the band where open pools start showing up and the rock takes on heat damage. None of these drop when you break them, so the crafted item is the only version you can actually carry home.

Placed by hand it keeps enemies from spawning in front of it, which the generated original never did, so re-walling a deep cavern base with your own stock is a real safety change and not just decoration.

Look-wise Obsidian Wall is flat dark stone that sits quietly behind furniture, while Ember, Cinder, Magma and Smouldering Stone carry glowing cracks and read as heat. Those four suit forge rooms and hell-themed builds; the plain obsidian version is the one to use when you want the background to stay out of the way. On the oldest console builds and the 3DS version only the obsidian pattern exists at all.