Unfathomable Darkness is a medium armor set. When you deal damage, you have a 10% chance to call a murder of crows around you for 12 seconds. Every 3 seconds a crow will be sent to peck the closest enemy within 12 meters of you, dealing 4000 Physical Damage. This effect can occur once every 15 seconds.
Unfathomable Darkness is part of the Clockwork City DLC and drops in Clockwork City in the Overland content. You can also find it on Guild Traders. Each set item is bound on equip. You can acquire medium armor, jewelry and weapons for this set in the Ebonshadow motif style.