Nikaea System

The Nikaea System is the star the Emperor terraformed so the Legions could argue about psykers in an amphitheatre. The edict that came out of it banned sorcery, chained the Librarius, and told Magnus to stop. He did not.

A later hunt for a shard of Magnus brought Thousand Sons and Space Wolves back to the same stone. This is the Council world, not a random Solar agri pin.

The Nikaea System still matters because the Imperium's psyker law was written here. Unofficial fan summaries keep the Segmentum Solar parent.