>>40524919 (OP)Those who seek the grail are already knights. That is, they have already been initiated into the mysteries of Jesus Christ by baptism and have begun the struggle against sin. This is why they are knights - they actively engaged in askesis against sin. They have begun the journey and fight, they have left the castle - that is, the "slumbering" state of the baptized who have not yet begun the Christian life in earnest.
The goal of this ascent is illumination, transformation and mystical union with Christ.
This is why the grail is gold. Gold is the Biblical symbol of goodness and worth. It is the alchemical perfect element and the symbol of perfect synthesis.
The grail is Christ Himself - by lore the literal archetype (first example) of His body and blood in the holy Eucharist.
It is illuminated and represents illumination as a symbol for the Uncreated Light seen by all the ancient fathers and modern saints.
You attain the grail by beholding the Uncreated Light. Katharsis--Theoria--Hesychia--Theosis.