Reposting from John J. Reilly's article on Martin Heidegger's Being and Time
Parallels can be found in the similarities between elements of Heidegger's system and that of esoteric Tradition, principally though not exclusively as represented in the philosophy of Heidegger's contemporary, Rene Guenon. Both were convinced that Plato roughly marks the point where Western philosophy departed from the contemplation of Being in order to gossip about the eternally expanding vacuum of mere ideas. Both had a horror of mechanism and quantification, and of what the modern world's embrace of these principles meant for the future. (Guenon's apocalyptic masterwork, remember, is called The Reign of Quantity and the Signs of the Times.) Parallels show up even in the details of their work, such as their insistence that time and space are meaningful in a way that geometry and clock-time simply caricature. Both were oddly fond of the adjective "primordial," at least if their translators are to be believed.
And then, of course, there is Julius Evola, sometime ideologist for Fascist Italy, and by most accounts the black sheep of the Traditional family. His system almost seems like Heidegger re-expressed in alchemical terms. Evola's formula for immortality involved not just resolution towards death, but the resolution to actually die. His late work, Ride the Tiger, is about the cultivation of the authentic self in a world where history is breaking down. By any reasonable reading, it is a form of existentialism, with only residual esoteric content.