The outer wings of this format are always intended as supporting pieces, often related to the main focus of the central panels but devoted to a single element of the theme. The sibyls themselves are directly related to the Annunciation.
There are spiralling ribbons that contain scripture that connects to Virgil. The rest of this carefully planned panel painting then features the sibyl kneeling down in draped clothing. An opposing artwork was also produced and placed along the other side of the altarpiece, which is titled as the Cumaean Sibyl.
The overall altarpiece can perhaps be considered Van Eyck's most famous artwork, alongside Man in the Red Turban and The Arnolfini Wedding. Each of these required considerable planning and several layers of execution as the oils were combined with other materials in order to create effects such as luminosity and transparency.