- "In the west of the Old World lies Bretonnia, a fabled land of honour and virtue, where noble Knights of the Realm keep their domains safe as their peasants till the fields, where Knights Errant strive to win their spurs in battle and where Questing Knights venture in search of the most holy of artefacts - The Grail. For it is said that to sup from this most holy chalice a knight will become more than just a hero, he will become a saint..."
- —The Kingdom of Bretonnia and its fabled Holy Grail.
The Cult of the Lady of the Lake, or simply the Cult of the Lady, is a state-official religious cult that serves to follow and uphold the values set upon them by the Lady of the Lake, and to serve the interest of her and the Kingdom of Bretonnia. Since ancient times, the Bretonnians have worshipped the Lady of the Lake as their goddess and their primary deity, a figure of myth and legend who guides their Kings and protects their lands from harm.
Worship of the Lady can be traced to the earliest days of the Kingdom. It is said that she arose from a Sacred Lake before Gilles le Breton and his Knightly Companions on the dawn of the Great Victory of Bordeleaux. Wreathed in a fey light, the Lady rose from the water bearing a Grail which overflowed with light that spilled into the waters of the lake, blessing the assembled knights until dawn's light broke over the mountains.
In the years that followed, Gilles and his knights went on to win many great victories and since those days, worship of the Lady has spread throughout Bretonnia. The lady herself is very rarely seen, and only in the most verdant depths of the land may she be found by a few privileged and pure souls. Those who do find her are regarded as highly favoured and are themselves revered.
Appearing as an ageless maiden of unearthly beauty, the Lady will only appear to those who have faced great peril and are pure of heart. Many knights, wishing to prove their valour, declare that they will go on a Grail Quest and seek the lady of the lake to sup from her sacred chalice and become one of the legendary Grail Knights, warriors of unsurprising skill who are incapable of malice and impure thought.
Sacred groves and areas of mystical power are her dwellings, and the magnificent Grail Knights are her protectors, devoting themselves to upholding her honour. No base creatures or evildoers can profane her sacred places, and this is a duty that every knight in Bretonnia, not just the Grail Knights, take very seriously indeed. The Bretonnian code of Chivalry is inextricably linked with the Lady of the Lake, as it is she who rewards honour and virtue, and the supreme sign of a knight's favour is to received her blessings.
Throughout Bretonnia there are many Grail Chapels built upon sites of holy significance, ranging from humble roadside shrines to great fortress cathedrals incorporated into a knight's Castle. It is the sacred duty of the Grail Knights to protect these shrines and often such knights will devote the remainder of their lives to defending the Lady's holy places. These knights are known as hermit knights and spend their lives living in and defending the shrines and relics housed within.
- 1: Warhammer: Knights of the Grail (FRP) - p. 36 - 40
- 2: Warhammer: Knight Errant (Novel) - Introduction