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
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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.
Notes
Anvil will upgrade a random weapon of yours each time you enter a shop. Once there are no weapons to upgrade, it will give you 2 Armor instead.
When acquired on Wildling, your weapons cannot be upgraded above Tier 2 by the Anvil, so Anvil will give you armor instead.
Arms Dealer will lose their weapons first when entering the shop, so will always get the 2 Armor.