grail or holy grail
grail / grāl
1. Grail, the cup or chalice used by Christ at the last supper, according to medieval legend, and was long sought after by knights due to its purported powers
The Grail was believed to have magic properties, although this idea was likely based on vessels from Celtic mythology that supposedly could satisfy the needs and wishes of anyone who drank from them.
www.artsandculture.google.com/story/the-search-for-the-holy-grail/YgXBHPuoCXhiag?hl=en, accessed March 30, 2023
2. (sometimes capitalized) something that is greatly desired and long sought after
Modern society, which, soon after its birth, pulled Plutus by the hair of his head from the bowels of the earth, greets gold as its Holy Grail, as the glittering incarnation of the very principle of its own life.
Karl Marx, 1818 – 1883