The Aeolian Abomination is is the first Shadowforged Armor alongside the Agni's Offering. It is doubly effective against Water armors, but doubly ineffective against Earth armors. The armor can be crafted with 12 Aeolian Crests. The Crests could be obtained through the limited edition Shadowforged Step chest or top prize in events.
From December 15th to December 22nd, 2016, materials for this armor can also be found in the last 4 stages of Heroic Mode -- Misty Marsh, Zephyr Plateau, Haunted Citadel and Kingdom of Darkness. After completing each stage, your reward is 3, 4, 6 and 11 Aeolian Crests, respectively, for a total of 24 (allowing you to craft this armor twice).