Seems to be related to Saturn worship:
Today, many people think that the Black Sun symbol is modern, only dating back to the early 20th century, after Nazi Germany incorporated a mosaic of it into the floor of Wewelsburg Castle in the 1930s (as shown below). But the Black Sun symbol is a very old one. Similar symbols can be seen in Zierscheibe (brooches dating back thousands of years). According to popular opinion, the Black Sun symbol at Wewelsburg represents Saturn. Some names for Saturn in ancient astrology were “Great Lord Dark Sun” and “Clothed in Black” and Saturn was referred to as the Black Star in ancient Judaic beliefs. In old astronomical texts, some cultures referred to Saturn as the Sun because there was once a time when it was closer to the Earth (see the Saturn Configuration Theory).
Quote from the NASA article The Ancient Colour of Saturn: “The colours that were traditionally assigned to Saturn in antiquity were black and yellow. Saturn today is yellowish. Why, then, was it called “black” in the Babylonian cuneiform texts and Greco-Roman writings? Some have wondered whether the enormous Phoebe Ring that surrounds Saturn today was once brighter. If so, Saturn’s appearance would have been that of a large black oval enclosed within a bright ring. According to Van Der Sluijs, ancient testimony supports the idea of a large “black” Saturn”. As well as calling Saturn “black” the Babylonians referred to Saturn as the Sun (as the “son of Shamash” and “star of Helios”). Given these facts, Saturn would have been considered the “Black Sun” to the Babylonians.
The Swastika became a symbol for the Black Sun. The Swastika is a very old symbol. The earliest Swastika was supposedly found in Ukraine and was dated back 12,000 years. In the documentary episode ‘Discourses on an Alien Sky#40’ David Talbott associates the Swastika symbol with the alignment of Saturn, Venus, and Mars that occurred thousands of years ago (again see the Saturn Configuration Theory). When Saturn, Venus, and Mars aligned, they went through various configurations and during a phase of intense discharging of light streaming from Venus, this planetary alignment took on a spinning Swastika-fashion, a form that various cultures around the world recorded as the Swastika and which became the basis for the Wewelsburg Black Sun design.
Paraphrase of Tracy Twyman: “The Black Sun is linked not only with Saturn, but also with the Boat of Ra [Saturn Ship]. According to David Talbott, the sky once looked very different than it does now. He proposes a pre-diluvian cosmology in which the dominant figure in the sky was Saturn. As [Saturn, Venus and Mars were in alignment and] moved closer to the Earth, a reflection created the appearance of a luminous crescent underneath Saturn. This, according to Talbott [was morphed] by the ancients into the “Ship of Heaven” and this, he says, was the Boat of Ra”. The Saturn Sun, Saturn Ship and Black Sun are all names for the celestial alignment of Saturn, Venus and Mars (which is known by various names and imagery because it went through various configurations).
Various researchers have associated the Black (Saturn) Sun with a stargate or worm-hole, now coined the “Saturn Stargate”. Miguel Serrano argues that the Black Sun was a worm-hole. This is echoed by Michael Jolta, who describes the Black Sun as “a worm-hole allowing for instantaneous travel across interstellar distances”. The Black Sun is also shown in Masonic Tracing Boards; see here (appearing to show the Black Sun as a gateway). As mentioned above, another name for the Black Sun was the Saturn Ship. This is because in ancient times when Saturn was in alignment with Venus, a luminous crescent formed underneath Saturn which was morphed into a ship; see here. Whether or not it’s a coincidence, the Saturn Ship resembles modern drawings of worm-holes.
In pop-culture, the Black Sun is often associated with a worm-hole or portal. In the video-game Wolfenstein, the Nazis discover how to enter the Black Sun Dimension through a portal to an incomprehensible outer dimension. In the comic book X-Men Black Sun, the story is based on opening a portal and in the video-game Remnant: From Ashes, the Black Sun is shown as a gateway, called the Black Sun Gate. Meanwhile in the TV series Space: 1999, there was an episode called the Black Sun. When they enter the Black Sun, they have a time-bending experience and are propelled a million light years away. In the video-game Trails of the Black Sun, the protagonist finds themselves in a simulation and must complete tasks, until eventually being released from the simulation.
In the image above from the video-game Trails of the Black Sun, the Black (Saturn) Sun is shown as an 8-pointed star. According to the Saturn Configuration Theory, when Saturn, Venus and Mars were aligned they went through various configurations, and at one point formed an 8-pointed star (recorded as the symbol of Shamash). The Black Sun star in the video-game Trails of the Black Sun even has a circle inside it just like Shamash. Carrying on with the idea that the Black Sun was a worm-hole, there are accounts from the Mayan civilization of Quetzalcoatl emerging from an 8-pointed star worm-hole, as explained by Mayan scholar John Jenkins. In Mayan belief, a serpent rope (or worm-hole) emerges from the heavens, symbolized by an 8-pointed star.
When writing this post, I was surprised how little good information that there is about the Black Sun on the web. The Black Sun is very popular today, but it’s still very much shrouded in mystery. The Black Sun is fascinating, and whatever the Black Sun is, it’s interesting (and potentially revealing) that fiction often associates it with worm-holes. Even in the movie Interstellar, the black-hole by Saturn (which is a worm-hole allowing Cooper to travel to a new place) is a sort of Black Sun. Scholar David Talbott provides a compelling case that the Black Sun and Swastika can be attributed to the alignment of Saturn, Venus and Mars. If so, the important question becomes, when will this planetary alignment happen again and is it something that humanity has any control over?