The Spectre Key can be used to teleport to a private room in another dimension, unique to each player.
Once there, you can build and store items safely, and they'll remain there. Leave by either using the Spectre Key again or by clicking one of the Spectre Core blocks on the floor.
The room is 16 blocks wide and deep, and defaults to being 2 blocks tall internally. You can expand it vertically by using Ectoplasm on the Spectre Core blocks.
Each Ectoplasm increases the height by one. It will use the entire stack at once.
