The Gray Stalker is a hard enemy and the first type of Stalker Aya meets. The Combat Lights are useful because it causes it to not only drop from the ceiling but also become visible, allowing Aya to attack it easier. The Grenade Pistol is very useful against it because it will deal 200+ damage without Energyshot and can stun it partially, allowing Aya to get in more shots. It can inflict Confusion, so Metabolism is useful.