All four items needed for this quest can be found off the East coast of Moonshade Highlands. The Construct Heart Plating is looted from Crocodarian. The Dragonbone Scroll Case be looted from Bonesnapper. The Asphodel's Grave Flower can be looted from Laethana. The Promise (not to) Charm can be looted from Lord Oseptos. All objectives are underwater, so the presence of a Warden or items/trinkets that enable you to breathe underwater are useful. Turn in to Ruric.