Night Terror is a medium armor set. When you take melee damage, you deal 2000 Poison Damage to the attacker. This effect can occur once every 1 second.
Night Terror is part of the base game and drops in Stormhaven 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 Daedric motif style.