There are thirteen planets around Zodiaca fair, but only twelve species.
In ancient times, before they could talk or fly between planets, the inhabitants of the Zodiaca system would see flickers in the corner of their eyes, movement where nothing existed. They never saw it no matter how fast they turned, but everyone knew when it was there. The unknowable fear of their species that no matter how hard they tried to banish from their minds would never go away.
Sometimes, it was just a passing presence, and in some places the species of the zodiac system could all but sense its form. These places were avoided forever. They named this movement in the dark, the twitch in the lights, "ophiuchus". All twelve species. All twelve species, who didn't even know each other existed.
When the Zodiacs made contact, built radios that could reach out across the void and talk, they discovered that every species they met had the same ironclad conviction, the same knowledge that something was there when nothing could be found. For a while it was even thought that the psychic carcili were the cause of the strange phenomenon, which had become associated with snakes, but eventually the carcili admitted that they too experienced this horror, deep in their ocean homes. In the end, the species of the Zodiac could do nothing but take solace in the fact that they knew it was, at least, a real phenomenon, and not a fabrication or quirk of their species' brains.
This was less of a comfort when the zodiacs made contact with many new species, none of whom had the slightest idea what they were talking about.
While the phenomenom of ophiuchus is typically restricted to the creatures of the zodiac system, other species who are born there, or live long enough eventually begin to "notice" ophiuchus. It is still not known whether they are really experiencing ophiuchus or whether they are simply becoming conditioned to expect it by society.
When the zodiacs leave their system, they may still notice the flickers and the movements, even though those who have not lived there never will - unless there are enough of the Zodiacs. Places where enough of them gather are likely to "spread" ophiuchus to the area, resulting in a place where the feeling of the thirteenth is strongest.
• The original Council Station was planned to be constructed at the largest asteroid in the asteroid belt, but after the station was almost complete, the builders found the structure to have the strongest sense of ophiucus ever felt in the universe. As it was so strong some zodiac species even felt like they could touch it, they built a new station on the other side of the solar system.
• Ophiuchus is not a real species! It is a phenomenon. Who keeps putting it here?
• Ophiuchus is very, very real.
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