Dindrane was born into the house of King Pellinore, the great hunter whose obsession with the Questing Beast had cost him his life, and she was the sister of Sir Percival, the knight who would one day achieve the Holy Grail alongside Galahad and Bors. In the earliest tradition, the 13th-century Perlesvaus or The High Book of the Holy Grail, she is called Dindrane and lives in the Castle of Souls - the Grail Castle - with her mother Yglais, a sister of King Pelles and widow of Alain the Large, lord of the valley of Kamaalot. In that version, she was kidnapped by Aristor of Amorave, who intended to marry and behead her, but she was rescued by her brother Perlesvaus and lived out her days as a maiden in the Grail Castle. But the Dindrane who would become the Grail heroine belongs to a different and greater tradition, the Vulgate Queste del Saint Graal, where she is Percival's sister by their father King Pellinore and where her story is one of active questing rather than passive rescue.

The defining encounter of Dindrane's life came at a hermitage, where she met Sir Galahad, the purest knight who ever lived and the son of Lancelot and Elaine of Corbenic. Galahad was hesitant, uncertain of his path, and Dindrane persuaded him to accompany her on the next stage of the quest. She provided a new girdle for the Sword of the Strange Belt, the great weapon that hung in the Ship of Solomon, and she fashioned that girdle from her own hair, an act that symbolised both her devotion to the quest and her renunciation of worldly vanity. When the two travellers reached the coast, they found a white ship waiting for them, with Percival and Bors already aboard. It was the Ship of Solomon, the vessel that had been built by the wisest king and enchanted by the demons he had bound to his service, a ship that could sail without wind or crew and that carried the history of the Grail in its very timbers. Dindrane boarded it as naturally as any knight, and she proceeded to interpret the relics and inscriptions that the men could not understand, revealing the history of the Tree of Life, the origin of the Sword, and the meaning of the sacred objects that surrounded them.

The quest led the four companions to a castle ruled by a leprous lady, a woman whose disease was so advanced that no physician could cure her. The knights of that castle told Dindrane that their tradition demanded a bowl of her blood to satisfy their custom, and when she refused, a battle broke out between the questers and the castle knights. The Grail companions were victorious, but that night they learned the terrible truth: the lady of the castle was dying of leprosy, and only the blood of a pure virgin who was the daughter of a king could save her. Dindrane, filled with pity and knowing exactly what the sacrifice would cost her, agreed to give her blood. She was a maiden, she was the daughter of King Pellinore, and she was pure in heart and body. The bloodletting began, and as the bowl filled, Dindrane's life drained away with it. She did not hesitate, she did not complain, and she did not ask to be spared. She asked only that prayers be said for her soul.

Before she died, Dindrane gave her last instructions with the clarity of a prophet. She told Percival to place her body in the white ship and set it adrift upon the sea, for she would be found again in the holy city of Sarras, the distant land where the Grail would finally be achieved. She foresaw that Percival and Galahad would die soon after her, and she instructed the three knights to part company until they found each other again at the castle of the Maimed King. Then she yielded up her spirit, and the grief-stricken Percival wrote an account of her life and adventures, placed it beside her body on the ship, and set the vessel to sail. The ship carried her without crew or rudder across the sea to Sarras, where her body was found incorrupt and pure, as if sleep had taken her rather than death. Galahad and Bors buried her there, and when Galahad himself achieved the Grail and healed the Maimed King, he too died and was laid to rest beside her, followed by Percival, so that the three Grail achievers and the Grail heroine were united in death as they had been in quest.

The legacy of Dindrane extends beyond the Vulgate Cycle into every retelling of the Grail story. In the Italian Tavola Ritonda she is called Agrestizia, and her role is identical: the sister, the guide, the sacrifice. In Thomas Malory's Le Morte d'Arthur, based on the Vulgate Queste, she is unnamed but unmistakable, the woman whose "seizure of power and agency" marks her as one of the few female characters in Malory's world who acts with the same autonomy as Morgan le Fay or Nimue, but in the service of good rather than enchantment. Later readers and writers have reclaimed her as the Grail Heroine, the forgotten fourth member of the Grail Quest, the woman who did not achieve the Grail herself but whose sacrifice made the achievement possible. Her body, incorrupt in Sarras, is the physical proof that the Grail was not merely a vessel of power but a mystery of self-giving love, and that the quest required not only the purity of Galahad, the innocence of Percival, and the witness of Bors, but also the blood of a maiden who gave everything she had for a stranger.