Empire of Sand
The bottle is made of brass and has intricate designs etched into it.
You discovered that this is an Efreeti Bottle containing a live Efreet. Drumph originally stole the bottle from a vault beneath the city. Damaceus Nadar offered to trade Tagrid some Potions of Longevity for the bottle. You made the trade, but followed Damaceus to a secret dungeon where you discovered he was part of a conspiracy to set Efreeti loose in Calimshan. You managed to get the bottle back from him, but he is still at large.
The bottle is currently located in Buttles’ extradimensional pocket.