The zrengi people of s'zod view the galaxy as a great machine, and the black hole at the center as a vast central gear, keeping the whole machine turning. All other functions of the galaxy turn on this central spinning gear. That is the premise of the galactic gear.
A very mechanically minded yet spiritual people, the zrengi revere this gear, and the makers of the tarot card deck adapted their iconography as an illustrative addition to the Major Arcana. It speaks to inter-connectivity and synchronicity. [link]
Another card for fun. Because these are pretty fun.