Ravenlord's Mantle is a Legendary/4-Star Spirit/Air armor from the Epic BossRavenlord. It is effective against water/earth types but ineffective against fire/earth types.
Gulfguard Marker Step Chest, Terrestrial Bulwark Chest, Fusion Tree Bling Chest, Limited Edition Shadowflame Ember Chest, Limited Edition Sentinel Mark Chest, Limited Edition Heroic Loot Chest (plus the normal chests including the Bossarmor Chest).