A dungeon owned by Brandin of the Isles (Brandus des Illes), lord of Doloreuse Garde, but in a separate castle from Dolorous Garde (Doloreuse Chartre). Every knight who attempted the adventure at Dolorous Guard and failed was thrown into the Dolorous Prison; their names, however, appeared on tombstones at Doloreuse Garde, as if they were dead. These knights included Yder, Guivret, Yvain of Leonel, Cadoain, Kehedin (Kahedins), Kay of Estraus, Girflet, Dodinel, Taulas, Mador, Galegantin, and Arthur’s son Loholt.
Gawaine was tricked into the prison by Brandin after Lancelot liberated Doloreuse Garde, but the lot of knights were eventually freed by Lancelot. Loholt and Galegantin developed serious illnesses while in the prison; Loholt later died, but Galegantin was healed by the Hermit of the Thicket.