Night Mother’s Gaze is a crafted set and is available in all armor types. When you deal Critical Damage you apply Major Fracture, reducing the target's Physical Resistance by 5280 for 6 seconds.
This debuff is the same that you get from other sources like the Piercing Armor ability or Noxious Breath.
Night Mother's Gaze is part of the base game. Crafting stations are located in Reaper's March (Old Town Cavern), Bangkorai (Silaseli Ruins) and The Rift (Eldbjorg's Hideaway). You need to have at least 6 traits researched (per item) to be able to craft this set. You can craft the set in any motif style that you know, and you can trade the crafted item pieces to other players. Each set piece becomes bound on equip.