Ebonbloom is a rare, metallic flower that grows in the caves below Mareth. They have special alchemical properties which allow them to be crafted into very protective armor. While the caves are inaccessible, they are rarely dropped by Basilisk or the Phoenix.
Ebonbloom, when examined You look over the Ebonbloom flower. It's rather pretty, outside of the fact that it reflects sunlight and blinds you. They're rare, so you're sure you could sell it if you wanted, though you can't help but wonder if there's another use for it.