The order decided a long time ago that they had to get rid of the mummy race. There was actually a race of aliens that looked like mummies and they almost took over the planet. A human was actually a witness to one of these alien lifeforms and this gave birth to the idea of wrapping humans in fabrics to make them look like these creatures. The real mummies used this cloths because the air and dust on planet Earth gave them allergic reactions. Not something that would be life threatening, but bad enough to make them want to cover their whole bodies up.
The order knew that they had to get rid of the mummy race when they all migrated to Earth thousands of years ago and planned to take over the planet. The order had them all annihilated by other alien life forms that served as assassins and then went back to their home planet. All mummies have been wiped out from Earth and from the universe at this point. Their planet of origin appears to be completely desolated, but there is no way of knowing if other mummies migrated to other planets.