The Runed Stygian cloth set is not a true set in that it does not provide set bonuses. The individual pieces provide bonuses to Stamina, Shadow resistance and Mana regeneration (MP/5). The stat bonuses on these pieces make this set attractive to Warlocks. These patterns are a random drop from a in-game mail you receive from Hermit Ortell. They are mailed to you a few hours after turning in Encrypted Twilight Texts to him.