I think this more reminds me of Zelda when it comes to this "Crystal Heart"
Crystal Empire: A Prosperous land of light and happiness. Also a empire from legend since it was gone for 1000 years.
King Sombra: A evil unicorn that comes to the land and blankets it in shadow and darkness. Not only that, but he enslaves the Crystal Empire and attempts to find the Crystal Heart. However, before he could find the power, Celestia and Luna banish him and turn him to shadow. Before he was sealed, he didn't want anypony else to find that power so he cursed the Crystal Empire and sent it through time to prevent Celestia and Luna from finding the power.
Heart Crystal: If a pony with a good heart uses it, it will bring lightness and happiness to the land. If a pony with a heart of evil uses it, it will blacken the land in shadow and darkness...
Crystal Empire :Hyrule/ Golden Land: King Sombra :Ganondorf Dragmire: Heart Crystal :Triforce: XD
I have this guess of what this guy's deal could be after looking the 8-minute teaser and episode summarys. my guess is that he was, in his childhood, the outcast of the crystal empire because he was the only one without a crystal like glittery shine and was scolded by some of the citizens and the servants of the palace. Sombra also could have be been abused by them as well, causing him build dark emotions which might have amplified by the crystal heart when he was near it and the heart fused with him, turning him into a reflection of his dark emotions, and then punished the crystal ponies by taking away their shine and torture them slave labor. Then when Celestia and Luna sealed Sombra in the glacier, the crystal heart sealed as well, and possibly caused the curse on the empire that made it disappear.
There's only one man I can think of who could voice this guy in my head, one single actor who could present the character as the cold calculating badass he should to be (and that I hope he is, not one of those cocky overly confident guys who talk too much). Jim Cummings man, who else could play this kind of character other then the guy who voice The Master from Fallout 1, or Scar from The Lion King.
He looks awesome!!!!! He looks looks cruel, sadistic, and badass. Who do you think should voice him? I know some pretty good choices.
Steve Blum Clancy Brown Scott McNeil David Kaye Kieth David Frank Welker Kevin Michael Richardson Daran Norris Chris Sabat Crispin Freeman Michael Ironside Corey Burton Jim Cummings John DiMaggio Mark Hamil D.C. Douglas Cam Clarke Chris Ayres Edwin Neil Tim Curry