There are a few mentions about “La Fontaine” in Chrétien’s Le Chevalier de la Charrete.
The Poisoned Fountain
Lancelot is on a quest to rescue Queen Guenevere, who has been abducted by Meleagant (Meleagaunce). He faces numerous challenges and trials along the way, showcasing his loyalty, courage, and determination. As Lancelot continues his journey, he comes across a fountain in a forest. This fountain is described as being located beneath the shadow of sycamore trees. The fountain appears inviting and serene, but it conceals a deadly danger.
Lancelot, feeling thirsty and fatigued from his travels, approaches the fountain with the intention of drinking from it. However, as he is about to take a sip, he is warned by a damsel who appears on the scene. The damsel informs Lancelot that the water in the fountain is poisoned and drinking from it would bring harm or death. She advices him to refrain from drinking and instead to seek water from another source.
Damsel of Noire Espine
After Lancelot had consumed poisoned water from a fountain and fallen gravely ill, the Damsel of Noire Espine had nursed him back to health. She had cared for him and helped him recover from the effects of the poison. This act of kindness and healing established a connection between Lancelot and the damsel.
Later in the story, Lancelot embarks on his quest to resque Guenevere. During his journey, Lancelot arrives at a “fontaine,” where he encounters the Damsel of Noire Espine once again. The damsel is in distress and being threatened by knights who are mistreating her. Lancelot, driven by his chivalric values and gratitude for her previous help, intervenes to rescue the damsel. He defeats the knights and ensures her safety.
The Vanishing Fountain
During Lancelot’s quest, he encounters a fountain in a forest. When he approaches the fountain and attempts to drink from it, the water suddenly vanishes as he reaches for it. This magical phenomenon frustrates Lancelot’s attempt to quench his thirst. After his initial attempt to drink from the vanishing fountain is thwarted, a maiden appears and offers her assistance. She tells Lancelot that the fountain’s water can only be obtained with the help of her own vessel, which she provides.
Source
Lancelot, or Le Chevalier de la Charrete | Chrétien de Troyes, late 12th century