The "Agartha" meme ("Himmler's favorite myth")

As reported in The Atlantic: 

Heinrich Himmler and other Third Reich occultists in the 1930s latched onto the strange idea that the Aryan race was not the product of evolution but descended from semidivine beings who left the heavens and established a secret civilization on Earth, possibly beneath Central Asia. Himmler, the head of the SS, was so enthralled by the possibility of what he considered celestial proof of the superiority of the white race that he provided funding for an SS expedition to Tibet in 1938 in the hope of locating his utopia, according to Black Sun, a 2001 history of Nazi occultism by the British historian Nicholas Goodrick-Clarke.

Almost a century later, this idea of a lost Aryan civilization, called Agartha, has caught on again, this time with teenagers posting memes online. If you’re older than 25, you likely missed it. But over the past year, memes about Agartha—a mystical, underground city in the center of the Earth full of flaxen-haired, blue-eyed people—kept going viral and have become a staple of the youth internet...

Agartha memes usually feature supercuts—a video of short clips—comprising UFOs in the Antarctic, pyramid-laden civilizations, digitally altered images of Charlie Kirk with blond hair and chiseled features, stereotypical Nordic-looking people, and sugar-free Monster Energy drinks in white cans... But all of the Agartha memes share in common the concept of the subterranean Aryan paradise that Himmler yearned for...

Agartha was first developed as a mythical fantasy by French writers in the late 1800s but had no far-right associations at the time. After Himmler co-opted Agartha, neo-Nazis carried it and other Third Reich racist myths into the postwar era by creating a new philosophy and value system called “esoteric Hitlerism,” a fusion of racialist ideology and wacky mysticism. In the early 2020s, white supremacists turned those myths into internet propaganda...

Sellner positioned the memes as something that could be taken in jest. “Irony is the glue that holds this whole meme-universe together. Anyone who takes things deadly seriously or gets triggered has lost,” he wrote. This is the tone that a lot of people online have taken regarding the Agartha memes. No matter the underlying content, you’re not supposed to take the joke seriously, and if you do, the joke’s on you.

It’s a well-worn tactic, but also a common excuse used to launder noxious content. It’s not ironic or satirical for ethno-nationalists to joke about a mythical ethno-state when that fantasy is reflective of their extreme beliefs.

Editorial note:  the word is AgaRtha, with an "R", not Agatha (and there is a Wikipedia entry with lots of info).