Aster Strongbox Key?

You can begin the "Aster Inheritance" quest by acquiring ether of the two Aster twin's Amulet's from their respective graves, or by finding the scroll "Finding the Aster Inheritance" in Corgan Hold.

Heric Aster's Grave is located South, South-West of Helmgard Keep, against the Western base of Skycrown mountain. Once your in the area you'll be able to spot the chest sitting at the foot of one of the small thing tree's you see around there. There will also be a Eel Petal plant and a Embereyes plant a couple of feet away on ether side of it. Note that the Grave's may be hard to notice due to the fact that they are just large stones.

Bodan Aster's Grave is located South of Dolve Wayle in the Tala-Rane section of the Plains of Erathell. The grave is particularly difficult to spot due to the fact that it's nestled in a corner on the north side of an old caste wall. There is a bright Edelweiss plant in the same area as the grave which may be easier to spot first. Additionally there is a Tala-Rane Lore stone nearby too.