The Holy Grail (more accurately, the Holy Chalice) is the cup which (according to the Gospels) Jesus Christ used at the Last Supper to serve the wine. According to the medieval legend, this cup was subsequently used to collect Christ’s blood that was shed on the cross (after he was pierced with the Holy Lance).
Some historians claim that because Jesus and his disciples were not exactly wealthy (to put it mildly) the cup was obviously made of wood and consequently could not have survived for two millennia.
Others contend that Jesus had some wealthy admirers (e.g. Joseph of Arimathea who is actually a perfect candidate) who could have provided (and did provide) even a golden cup for ceremonial purposes. Consequently, it is possible that the Holy Chalice did, indeed, exist. Maybe still does.
It is also possible that someone (most likely, the same Joseph of Arimathea) brought the cup to Golgotha precisely to collect blood of Jesus that he believed to be sacred (in other words, to have spiritual powers).
Because of this belief, some Christian mystics (and many occultists) believe that the Holy Chalice was imbued with supernatural (magical) powers.
In the ersatz-religion of national-socialism, blood (explicitly or implicitly) had spiritual (to Himmler – even magical) powers as well. He also believed (as did many of the leading Nazis) that Jesus Christ actually was not Jewish, but of an Aryan stock.
Given the fact that it is highly problematic to even try to establish the nationality of the Son of God (and that eventually Christianity became religion of Gentiles), that belief was as good as any.
Consequently, Himmler considered the Holy Chalice to be an occult artifact that possessed some serious magical powers. And given the belief that it was in contact with a sacred blood of the Son of God, he considered these powers sufficient to bring Germany victory in World War II (and in the whole existential war) and subsequently world domination.
Therefore, it is not surprising at all that SS Reichsfuhrer spend considerable amount of money, time and other resources attempting to find the Holy Grail.
For this project he initially commissioned one Otto Rahn – a colorful character (he is considered as the inspiration behind the famous Indiana Jones character), a German historian, archaeologist, medievalist, Ariosophist who at that time despite his young age was considered a leading authority on Holy Grail.
From an early age, he became interested in the legends of Parzival, the Holy Grail, Lohengrin and the Nibelungenlied. While attending the University of Giessen, he was inspired by his professor, Baron von Gall, to study the the Cathar heresy and the Albigensian Crusade of the Holy Roman Catholic Church.
Rahn wrote two books (published in 1933 and 1937, respectively) linking Montségur and Cathars with the Holy Grail (which meant that the former was the right place to look for the latter).
Rahn argued that there was a direct link between Wolfram von Eschenbach’s Parzival and the Cathar Grail mystery. He believed that the Cathars held the answer to this sacred mystery and that the Holy Grail was hidden somewhere beneath the mountain peak where the fortress of Montségur is located – the last Cathar fortress to fall to Catholic Crusaders.
Rahn’s books attracted Himmler’s attention and somehow convinced him that Otto Rahn – if provided with adequate support from the SS – will be able to find the Holy Grail for him.
So he made Rahn an offer the latter simply could not refuse. To continue his research, he needed money – and a lot of it. For some unknown reason (probably to have a better control over Rahn), Himmler made him join the SS without usual careful vetting.
This decision turned out to be a huge mistake because Rahn was homosexual and half-Jewish. It was inevitably discovered and contributed to subsequent downfall and suicide of Otto Rahn.
Rahn predictably failed to find the Grail and after running out of money, had to return to Berlin empty-handed. This failure delivered a devastating blow to his self-esteem, he started to drink heavily and after a drunken homosexual scrape was assigned (as punishment) to guard duty at the Dachau concentration camp.
Brutality that he witnessed on a daily (if not hourly) basis and inability to do the only thing that he loved – historical research – made him resign from the SS. Which did not help much – in March of 1939 he committed suicide (or was murdered on Himmler’s orders).
This failure, however, did not stop the Reichsfuhrer. After carefully studying Richard Wagner’s opera Parsifal (some historical research), he came to a conclusion that Holy Grail was hidden not at Montségur (as Rahn had claimed), but at famous Montserrat Abbey near Barcelona. And decicded ot take this matter (apparently vitally important to him) into his own hands.
In 1940, Himmler accompanied Hitler on his trip to Spain (Führer unsuccessfully tried to convince Spanish dictator Francisco Franco to enter World War II on the German side). He visited the abbey and asked Andreu Ripol Noble – at the time the only German-speaker in the abbey to help him with his quest for the Holy Grail.
However, he came back from Montserrat empty-handed. Most likely, because the Holy Grail was simply not there. And for a very good reason – if it was not lost during the first turbulent centuries of the Christian Church (which was highly likely), it was most probably taken to Rome which soon became the global capital of the Christian Church and possibly is still hidden there (maybe even in the Secret Archives of the Vatican).
After his failure in Barcelona (and because Germany was fighting a war), Himmler apparently decided that he had no time, money or other resources to spare on this quest. So he made no new attempts to find the Holy Chalice.