Decay Chamber

Every piece of corruption furniture runs through this station and nothing else makes it. The Steampunker only lists it if your world rolled corruption, so crimson players have to come at it sideways, either through Shimmer or by crafting across from the crimson version once they own that.

The dependency that actually catches people is upstream. The chamber works on lesion blocks, and lesion blocks come off a Meat Grinder, so buying this first leaves you with a station and nothing to feed it. Sort the grinder out before you spend the gold. Once both sit in your build room the whole corrupt furniture line opens at once, which is enough for a full themed house.