Perfect was Gweir's prison in the Faery Fort.
Due to the ministry of Pwyll and Pryderi
none before him had entered therein.
In the heavy blue chain a faithful servant kept him
and for the Spoils of Annwfn keenly he chanted
and unto Doom shall continue in bard-orison.
Three fulnesses of Prydwen we entered in:
Save for seven none came up from Fort Faery.

Book of Taliesin (c. 1275?) - The Spoils of Annwn