Spider Wall

The Spider Wall is a background wall found naturally generated in Spider Nests, where they are considered unsafe. The player can create safe Spider Walls via crafting, and unsafe Spider Walls by placing  (obtained by throwing a crafted Spider Wall into Shimmer).

Unsafe Spider Walls will drop nothing when destroyed with a hammer. They can spawn Wall Creepers in pre-Hardmode and Black Recluses in Hardmode, and therefore cannot be used for proper housing. They can create Cobwebs over time, with a chance to yield a Cobweb item when destroyed. Infested Spider Walls, visually identical to Spider Walls, can be placed to enlarge an existing Spider Nest, or create a new one.

Safe Spider Walls are crafted. Like other craftable walls, they drop as an item if destroyed with a hammer, and do not spawn enemies once placed, making them suitable for housing. They do not spawn Cobwebs nor contribute to a Spider Nest biome.

Trivia

 * On the background texture of the wall there seems to be a bound NPC. This could be a reference to the actual Lost Girl, or more likely the Stylist NPC as she will initially spawn (bound before rescue) within a Spider Cave.