Lihzahrd Furnace

The name is misleading. It smelts nothing. All it does is unlock the temple furniture set, and it will not even handle the matching wall, which comes off a work bench like any other wall in the game.

One sits in every chest inside the temple, so it is never something you have to hunt for. If a temple room happens to have generated open to the outside, you can walk in and take one long before you have any business being down there. Once Golem is down the Steampunker will sell copies while she is living in the jungle, which is the painless way to get a second for another base.