Masque of the Morning Stars
In M42, they protected the remains of an ancient Aeldari civilization on an unnamed world, from the landing parties of the Rogue Trader Archiroxus Belledar XVII and Inquisitor Philemon Mar. The two had sought to investigate the ruins, but the Masque ambushed their forces after they landed on the world. By utilizing their knowledge of the terrain and acting independently, the Harlequins has made it impossible for the Imperials to predict their movements and formulate an effective response.
- 1: Warhammer 40,000: Kill Team Core Manual (3rd Edition) Core Book, pg. 21 - Theatres of War