Deheubarth is Pryderi’s southern realm, a territory defined by its twenty-one cantrefs and drawn into the political maneuvering of Math’s court. It is presented both as a structured domain and as one of the kingdoms whose mobilization Gwydion proposes to exploit.

Territory and Divisions

The account assigns Deheubarth twenty-one cantrefs under Pryderi’s rule. Seven belong to Dyved, seven to Morganwc, four to Ceredigiawn, and three to Ystrad Tywi. This enumeration gives the southern realm a specific administrative shape, distinguishing it from the northern kingdom of Gwynedd, which is ruled by Math.

Rule and Political Context

Pryderi, son of Pwyll, is named as lord of Deheubarth. The narrative places his authority alongside Math’s rule over Gwynedd, establishing two regional powers before Gwydion’s schemes set their courts in motion. Deheubarth is thus introduced through both its ruler and its place within the wider political geography of the story.

Role in Gwydion’s Plan

When Gwydion seeks a pretext to get Goewin away from Math’s court, he promises Gilvaethwy that he will cause Gwynedd, Powys, and Deheubarth to rise in pursuit of the maiden. The proposal treats Deheubarth as one of several powers whose collective mobilization could create the disruption needed for Gwydion’s plan. The account does not describe the realm’s inhabitants or political response in this passage; its immediate significance lies in its inclusion among the kingdoms Gwydion intends to draw into the crisis.