Masks were closely associated with Dionysos. They acted as both a symbol of his presence and his cult image, frequently appearing in rituals associated with the god.
Masks represented the transformative power of Dionysos, allowing the wearer to set aside their own identity and change from male to female, young to old, or from human into a god or an animal.
As the god of masks, Dionysos is also the masked god. The true face of Dionysos is never revealed to us.
The presence at Attic symposia (drinking parties) of kylikes (drinking cups), decorated with two pairs of large eyes, added an element of theatricality. As the cup was lifted and tilted towards the drinker, the handles became ears and the foot became the mouth. Together with the eyes, these cups acted as masks, concealing the identity of the drinker to the viewer.
The god - what did he look like? You claim you saw him clearly. He looked as he wished to look. I had no say in the matter.
- Euripides, Bacchae, 477-8
The drinker himself was often confronted with a gorgoneion, the frightening face of the Gorgon Medusa, as he emptied his cup, perhaps serving as a reminder of the dark power of the mask. Eye cup exteriors commonly featured Dionysiac imagery, fitting with the theme of the symposia and the function of the vessels.