The Bloody Grail and the dark lady.
The history of the Knights of Bretonnia includes much that may be the influence of Blood Dragons or other Vampires. In 1813, Duke Merovech of Mousillon was censured by the king for his cruelty in keeping criminals impaled in his dining room. The duke responded by challenging the king to single combat. Merovech won, tore out the king’s throat and drank his blood from a goblet. Horrified, the other lords waged war on Mousillon and annexed much of its land. Four hundred years later, Duke Maldred, lord of what remained, claimed to have found the Grail of the Lady and had all his knights drink from the wine that flowed from the heavy silver cup. The grail was proved false, and Maldred was routed and Mousillon prohibited from having a lord ever again. But the cup’s liquid appeared to give Maldred’s knights an unholy strength, and few Vampire hunters believe in coincidences.
Other knights also talk of being visited by the Lady of the Lake in their dreams, only this Lady is clad in dark robes and offers a grail full of blood-red wine, explaining that she must prepare the knights for the blood they soon will be called upon to spill in her name. Most do not drink. Most, but not all.
Source
- Warhammer Fantasy RPG 2nd ED -- Nights Dark Masters (pg. 51).