I think That keyblade looks like the Keyblade Riku used in kh1 to unlock hearts
You know, the two things that cross look a bit like.. Keyblades. Dead heart (VAT's idea)+ my idea of sorts = Dead Heart of a Keyblade Master/ Keyblade (said, to something like a heart).
Possible idea.. when a keyblade (or keyblade master).. somehow dies (gets killed) and one of these creatures is formed.
Edit (hmm..):
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