"Culvert" is the official title for one of the natural mob spawners. Although its game id tag is "pipe," and some in-game notifications refer to it as such (for example, the description of the Pest Control achievement), players tend to call it a round maw, a gold maw, an automata maw, a mechanical maw, or just a maw. A culvert is a more dangerous version of a regular maw. It appears as a dark round hole surrounded by a circular brass ring.

Typically, culverts spawn both large and small automata, and occasionally, adult brains. In hell worlds, however, they spawn only adult brains (and no automata at all), and in brain biomes, they often spawn baby brains in addition to, or sometimes instead of, automata. In unpurified deep biomes, meanwhile, culverts periodically explode and spew poisonous gas.

Culverts and maws are found underground on background earth in all biomes.

How to Obtain

This item cannot be obtained into player inventories.

How to Use

  • Culverts are an important part of mob farming, especially in hell worlds.
  • In temperate biomes, hanging around a culvert and killing off the automata as they spawn is a great way to get the recycler achievements.
  • Culverts are plugged with the same plugs you use to close off regular maws.
  • In deep biomes, the world must be purified before you can plug a culvert. Attempting to plug a culvert before the world is purified will result in a small explosion that destroys the plug.
  • Once plugged, a culvert becomes part of the background and cannot be unplugged. You can, however, excavate plugged culverts with a properly-equipped butler bot and the appropriate automata skill level.


Early on in the game, it wasn't possible to excavate plugged maws or culverts. As a result, when visiting old builds, you'll sometimes see a random plugged culvert in an otherwise fully excavated area.