Dark Stone
From Wikimon
The Dark Stone in "Resurrect! The Appearance of All Seven Death Generals!!"
The Dark Stone (ダークストーン Dāku Sutōn) is an item which is key to D5 that appears in Digimon Xros Wars: The Evil Death Generals and the Seven Kingdoms. Dark Knightmon uses the negative energy gathered from each Land to transform the Code Crown into it, infusing it with the power of darkness.
