Depth Meter

Informational accessories work from anywhere. Leave the Depth Meter loose in your inventory, in a Void Bag, or in a vanity slot and the readout still appears. The only thing you give up by not equipping it properly is the modifier. In multiplayer the reading is shared with teammates standing near you, so one person carrying it covers the whole group.

Zero is the line where the Surface ends and the Underground begins, not sea level. That catches people out, because the two oceans in a world are rarely level with each other and both usually sit well above the zero mark. Alongside the figure it names the layer you are standing in, which is often the more useful half. What makes it worth carrying is that the world generates in altitude bands. Floating Islands sit at a consistent height, the Underground Jungle occupies its own range, the Underworld starts at a fixed depth, and the first three Hardmode ore tiers each favor a band. Note the depth where you found one and the next is a matter of tunneling sideways at that number instead of wandering.

Dungeon Guardians appear if you push into the Dungeon proper below zero depth before Skeletron is dead. Watching the meter is the simplest way to loot the upper rooms early without being deleted for it.