When the planet Thagra IV was invaded by the Alpha Legion, the White Panthers were sent to liberate the planet. The planet had a heavy mutant population, involved as the slave workforce within the planet's manufactoria. During the rebellion many of the mutants joined the Alpha Legion's attacks, while some remained loyal and resisted the invasion through guerrilla warfare. The White Panthers eventually drove the Alpha Legionnaires off, afterwards rounding up most of the mutants, including those who had fought against the invading Alpha Legion, considering them all to be traitors. Ready to execute the entirety, the Inquisitor Gregor Eisenhorn forced the Space Marines to have the loyal mutants spared.
- Inquisitor Rulebook — Mutants section