German writer, medievalist, Ariosophist and an Obersturmführer (First Lieutenant) of the Nazi Schutzstaffel (SS), who researched grail mythos.
Speculation still surrounds Otto Rahn and his research. 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 Albigensian (Catharism) movement and the massacre that occurred at Montségur. Rahn is quoted as saying that “It was a subject that completely captivated me”.
Rahn wrote two books linking Montségur and Cathars with the Holy Grail: Kreuzzug gegen den Gral (Crusade Towards the Grail) in 1933 and Luzifers Hofgesind (Lucifer’s Court) in 1937. After the publication of his first book, Rahn’s work came to the attention of Heinrich Himmler, the head of the SS, who was fascinated by the occult and had already initiated research in the south of France. Rahn joined his staff as a junior non-commissioned officer and became a full member of the SS in 1936.
Openly homosexual, frequenting anti-Nazi circles, and having fallen out of favour with the Nazi leadership, Rahn was assigned guard duty at the Dachau concentration camp in 1937 as punishment for a drunken homosexual scrape. He resigned from the SS in 1939.
But the SS would not allow anyone to resign without consequences. Soon, Rahn found out the Gestapo was after him, and he was even offered the option of committing suicide. He vanished. On 13 March 1939, nearly on the anniversary of the fall of Montségur, Rahn was found frozen to death on a mountainside near Söll (Kufstein, Tyrol) in Austria. His death was officially ruled a suicide.

Link to Wikipedia biography