Cornerstones are persistent home bases that travel with you between worlds. Claim your cornerstone, make it your own, and move it to wherever your heart desires. In addition to being able to build a place to call your own, you’ll also respawn at your Cornerstone once you’ve claimed an area.
Claiming your Cornerstone
Your cornerstone acts as your home base while you're adventuring and in a Hub. In order to build in your cornerstone you must first claim it. To claim a cornerstone find one of the dark gray pads with signposts next to them. If the signpost has a question mark, then that cornerstone plot is un-claimed. To claim it, press the E key on the sign. Once you have claimed the cornerstone, an arrow will appear that indicates that the game is loading your cornerstone. You cannot build on a loading cornerstone, though you may use objects that were already present on it. Once it changes to an exclamation point, that means it finished loading and you can build. Cornerstones are protected, so only the owner can add to or remove from them.
Cornerstones are 16 blocks wide by 16 blocks long. You can dig 50 blocks down from ground level and build up 150 blocks. Any blocks within that 16 x 16 x 200 space will be transferred as part of your cornerstone.
You can add blocks such as Spikes or Horizontal Jump Pads (facing away from your cornerstone) to prevent enemies from entering. Alternatively, you can build your cornerstone elevated from the ground, as most enemies cannot jump to reach you. This will not work with bosses with the teleport modification.
These techniques can be exploited to automatically kill shadow giants without actively fighting them, and are often used during special events that replace them or increase their spawn rate.