A magical spring in the Forest of Serpents that healed all who drank from it.
It was formed when Nascien, a follower of Joseph of Arimathea, stuck his lance into the ground prior to a battle with the evil King Camalis. It flowed next to the Giant’s Tower, and Sir Atamas, also called the Knight of the Spring, ruled them both.
Atamas used the power of the spring to defeat any knight who came along: he drank from it in mid-combat, thus invigorating himself while his opponent remained weak. In this manner, he defeated and imprisoned Gawain and many other knights in the Giant’s Tower. Palamedes (Palomides) ended the practice by defeating Atamas despite the power of the spring.
Source
Post-Vulgate Queste del Saint Graal | 1230-1240