Part of the Grail mythos is that Joseph of Arimathea took the chalice Jesus used at the Last Supper and caught the blood of Christ as it flowed from the Cross. (You can read some background by the always interesting John Matthews here.) Some of this blood also touched the ground at Golgotha. As Rudolf Steiner argues, “This one event, the flowing out of the blood from the wounds, is at the same time the greatest cosmic upheaval in earthly existence.”
So this cosmic upheaval going on in the heavens right now is reflected in the event that is always already happening at this time of the year: The Mystery of Easter. That’s like two cosmic upheavals at the same time.
For Steiner, the cosmic upheaval at Golgotha is the defining moment for all human and earthly life. As he describes it,
“This physical event — the occurrence on Golgotha — is the expression, the manifestation of a spiritual event which stands at the central point of all earthly happenings. Anyone interpreting these words according to the present materialistic world concept will not be able to make much out of them, for he will not be able to imagine that at that time something occurred in this unique Event of Golgotha which differs from some other like event, or from one perhaps physically similar. There is a very great difference between all the earthly occurrences which preceded this Event of Golgotha and those that succeed it.”
Steiner on the Grail Moon:
“Now before we go further and try to interpret this sign in the heavens, I must draw your attention to an important law, an important fact. The gold-gleaming sickle becomes apparent because the physical rays of the sun fall on the moon. The illuminated part of the moon shines out as the gold-gleaming vessel. Within it rests the dark Host: physically, this is the dark part not reached by the sun’s rays; spiritually, there is something else. When the rays of the sun fall on part of the moon and are reflected in gleaming light, something does nevertheless pass through the physical matter. This something is the spiritual element that lives in the sun’s rays. The spiritual power of the sun is not held back and reflected, as the sun’s physical power is; it goes through; and because it is resisted by the power of the moon, what we see at rest in the golden vessel is actually the spiritual power of the sun. So we can say: In the dark part of the moon, we are looking at the spiritual power of the sun. In the gold-gleaming part, the vessel, we see reflected the physical power of the sun. The Spirit of the sun rests in the vessel of the sun’s physical power. So in truth the Spirit of the sun rests in the vessel of the moon. And if we now recollect all that we have ever said about this Sun-spirit in relation to the Christ, then in what the moon does physically an important symbol will be manifest. Because the moon reflects the sun’s rays and in this way brings into being the gold-gleaming vessel, it appears to us as the bearer of the Sun-spirit, for the Sun-spirit appears within the moon’s vessel in the form of the wafer-like disc.
“And let us remember that in the Parsifal saga it is emphasised that on every Good Friday, and thus during the Easter festival, the Host descends from Heaven into the Grail and is renewed; it sinks into the Grail like a rejuvenating nourishment—at the Easter festival, when Parsifal is again directed towards the Grail by the hermit; at the Easter festival, whose significance for the Grail has also been brought nearer to mankind again through Wagner’s Parsifal.”
Sergei Bulgakov also sees the mystical connection between the Grail and the Mystery of Golgotha:
“We thus arrive at the unexpected conclusion that Christ, who ascended to heaven and departed the world, abides in the world in His blood and water—and He abides not mystically (as in the eucharistic elements), secretly, invisibly to human eyes, but essentially and really…. This abiding is not a sacrament, for sacraments, despite all their mysteriousness, are always known, since they are linked to a definite place and time. Rather, this abiding is a mystery, the world’s great holy, divine mystery, the world’s treasure, holiness, and glory—the HOLY GRAIL….
“It is not surprising if this mystery, till now still unilluminated by the theological-dogmatic consciousness, has lived only in the obscure presentiments of Christian legend and poetry, in which the holy myth is clouded by human imaginings, by romantic reveries. But at the appropriate time this mystery can take center stage in the Christian world’s consciousness, and then the holy treasure of Montserrat will catch fire with heavenly light and will lead the nations to meet the coming of Christ. The whole world is the Holy Grail, for it has received into itself and contains Christ’s precious blood and water. The whole world is the chalice of Christ’s blood and water; the whole world partook of them in communion at the hour of Christ’s death. And the whole world hides the blood and water within itself. A drop of Christ’s blood dripped upon Adam’s head redeemed Adam, but also all the blood and water of Christ that flowed forth into the world sanctified the world. The blood and water made the world a place of the presence of Christ’s power, prepared for the world for its future transfiguration, for the meeting with Christ come in glory…. The world has become Christ, for it is the holy chalice, the Holy Grail.”