A rhyton, or rhysa, is a ceremonial cup used for pouring libations or at state functions.  They are highly decorative and typically decorated with scenes of mythology.

As seen to the left, an example from the Panagyurishte Treasure:

The Panagyurishte treasure was unearthed by accident in 1949, during clay digging near the town of Panagyurishte. It has been dated to the fourth century BC. The find consists of nine solid gold vessels, decorated with different zoomorphic and anthropomorphic figures, including seven rhyta, a rare amphora-rhyton and a phiale. The amphora-rhyton, the four rhyta shaped like animal heads/fore-parts and decorated with mythological scenes, the three jug rhyta shaped like women’s heads, and the phiale decorated with representations of African men’s heads and acorns are all pieces of a ceremonial tableware drinking set that belonged to a Thracian king (presumably Seuthes III), from the end of the 4th and the beginning of the 3rd centuries BC. The inscriptions on the phiale and on two of the vessels refer to the town of Lampsak on the Dardanelles as the place where they had been made.

–information from the website: www.omda.bg/public/engl/history/panagyurishte_treasure.htm on Bulgaria’s Thracian Treasures.by