Leyak

The Leyak is Abiotic Factor's signature stalker, a hostile entity that begins haunting you after you reach the XR Containment area in Cascade Laboratories. She appears, vanishes, and harasses you across the facility. You repel her with X-Ray light sources, the X-Ray Tower or Lamp and their upgrades, or by keeping her in direct, unobstructed sight. Driving her off can drop Leyak Essence, a key crafting material.