Pots of Chance are special blocks that can be found scattered in both Caverns and Lake Caverns. They can also sometimes be found in Ruins, Abandoned Shacks, and Underground Ruins, and are always found in Cragrock Towers and the Wight Fortress. They spawn with a random item or two (can be stacked) already inside them. There are three different visual variations of them and have randomized rotation. When broken, they will drop the item that has been stored inside, as well as occasionally spawning a small Termite. Right-clicking an empty one with an item will also put the item inside.
A different type of pot can also be found at the bottom of the tar pool in Tar Pool Dungeons. These appear as normal Pots of Chance that are stuck inside Solid Tar blocks. They have the same properties as normal Pots of Chance and also generate with items inside them, but unlike normal they must be mined with a pickaxe.
See the Loot Tables page for possible loot to be found in generated Pots of Chance.