Digging Molecart

The Zoologist stocks it, but not straight away. She only puts it on the shelf once your Bestiary is a quarter filled, which is less work than it sounds: ordinary pre-Hardmode play plus a few deliberate fishing and critter trips gets you there. It is expensive relative to the point at which you can first afford it, and it is still worth the gold.

Ride it and it chews out a corridor tall enough to walk in while laying plain track behind itself. You need a pickaxe or a drill somewhere in your inventory and it will use the best one you own, plus a stock of ordinary track. Booster or pressure plate track in your bags does nothing for it. It only digs at Underground depth or below, and it only travels level, so starting it on a slope just straightens out immediately. It is slow out of the box, but a Minecart Upgrade Kit brings it up to the speed of every other cart, which changes it from a project into a commute.

Horizontal quarantine trenches. Vertical shafts are easy with explosives, but long level ones are not, and cutting them by hand or by buying Scarab Bombs is either slow or expensive. Run two or three subway lines across the world before you break an altar and the Corruption or Crimson has nowhere to cross when Hardmode lands. The same tunnels double as fast travel and as a ready made search corridor for the new ores, at exactly the moment the game is asking you to do six things at once.

Start a fresh line a few tiles below the last one and the cart clears the old track while it lays the new. Repeat that a few times and you have hollowed out an open box far faster than digging it, which is the quickest way to get an underground jungle arena ready.

Chests and other containers with anything inside them are a hard stop, and so are the blocks directly beneath any container, even an empty one, so those have to come out by hand before the line can continue. Using any item at all pauses the digging, so put the mouse down and let it work. It handles falling blocks now, but near the surface desert it is still worth advancing in short bursts and letting the sand break on the track you just laid, which turns it into items instead of dropping it on your head.

• Blocks it mines do not count toward the Bulldozer achievement, so do not plan on grinding that out from a cart.
• The track it places cannot be recolored with a Paint Sprayer.
• Creative Shock does not stop it, though you cannot pick its track back up while that debuff is on you.
• It digs a tunnel a tile taller than a cart strictly needs, which is convenient if you intend to walk the line as well as ride it.