Cavern

Cavern the gun came out of the 2019 Christmas Box, which was part of the 2019 Christmas Event and left with it. The box is gone, so the gun can now only be obtained by trading. The wiki lists it as a Legendary gun and also notes that it is considered to have low demand.

Look

The barrel and frame resemble an ice cavern, which gives the weapon its name. The tip of the barrel is white and fades into an icy blue along the frame, where large black patches sit. The accents and handle are solid black, and the handle has tape wrapped around it.

Pairing with the knife

It has a partner knife under the same name, Cavern (Knife), and together they make the Cavern Set. The knife came from a different source: it was the 29th tier of the Main Event, not a box drop.

A gap on the wiki

The pages do not agree with one list. The Legendary Weapons table includes Cavern (Knife) but leaves out Cavern (Gun), even though the gun has its own page that labels it Legendary. That looks like an omission in the table rather than a disagreement about the gun itself. The curated data also records a 5% chance for the Legendary slot of this box.