From Brotato Wiki
Stats
A random weapon is upgraded when entering a shop. If you have no weapon to upgrade, you gain +2 Armor instead.
Price
120
Limit
1
Unlocked by
Win a run with Arms Dealer
Item
Anvil is an in-game item that can be bought from a Shop or can be found in a Crate. Most Items modify the Stats of the player, and some of them provide additional effects.
Unique
Anvil is a unique item. Only 1 of each unique item can be equipped, and it will then no longer be offered in the Shop, and no longer drop from loot crates.
When acquired on Wildling, your weapons will be upgraded beyond Tier-2 (and you'll get armor instead).