from an astronomical point of view, Sedna is the most important object discovered in our solar system since Pluto, and possibly since Neptune. There is simply no current scientific model of the solar system's formation that allows it to be there. It's as if you had spent 5000 years assembling a million-piece puzzle, and found, after you had finished the picture, that there was one piece left over at the end.
To get an idea of how weird Sedna is, look at this Wiki image:
As you can see, it is completely separate from the rest of the system. It's as if some giant hand just decided to place it in orbit around our system as a joke. It's orbit is also unlike any other large object; it is in fact more like that of a giant comet. For a small fraction of its 12,000 year orbit, Sedna will be within a distance from the Sun comparable to Pluto or Eris, but within a few centuries it will fly out into the dark depths of space, until our entire system becomes just a dot on its horizon.
What kind of astrological power could such a peculiar object have? Since most of its time will be spent far away from the other objects in the system, how much influence could it exert? How would its strange and inscrutable nature affect whatever mystical power it might possess?