The Blessed Undead Slaying sets can be found during the Scourge Invasion world event occurring in Patch 3.0.2. The original Scourge Invasion saw the introduction of the original Undead Slaying sets. There are four sets, one for each armor type. The gloves and shoulders of each set are sold by the Argent Dawn in exchange for fifteen [Necrotic Runes]. The legs are Bind on Pickup and are dropped by rare spawns at the Necrotic Shards. The chest pieces are Bind on Pickup and dropped by Shadows of Doom which spawn when you disrupt the shard.