They should have stick with Shadow Lock design. Now we are left with some scrawny looking pony who apparently already had kids according to comics

Retagging due to leaks and confirmation

@MLPFiMFan2232  
That’s a pretty good choice,  
I think Paul Dobson would be perfect if he did something similar to his Demitri Maximoff from Night Warriors: Darkstalkers’ Revenge

I made a picture of him. You’d better check it out. Here’s the link: https://derpibooru.org/1449468

I could defiantly see Lee Tockar doing the voice for this villain. As long as he does something similar to his Makuta voice.

I dub thee…
 
KING GROMOS!

Could be a changeling progenitor. The origin account Queen Chrysalis (Princess Chrysalis?) gave seems to undermine that. Plus Shadowlock doesn’t look like a changeling I’ve ever seen. Making a giant pool of toxic green slime and hoping some squirrel will throw a rotten acorn into it is a pretty strange reproduction strategy. But hey, retcon.
 
Could be ‘Cosmos the Almighty’. Very bizarre look for an evil alicorn compared to Nightmare Moon. Plus, if Shadowlock is his descendant shouldn’t he be an alicorn too? Like Flurry Heart? Or have the alicorn genes become too diluted at this point? I’d say it’s likely he’s somewhat inspired by the idea of Cosmos but less likely a complete rendition of him.
 
I don’t think it’s Grogar because… Well it isn’t. I mean the writers can name him Grogar, and make it canon, but that’s not Grogar as he’s been known for 30 years. He’s not a ram, doesn’t have a bell and there’s no mention of Tambelon(or Bray, but he sucked anyway). Why would the MLP crew rewrite a perfectly good character with tons of nostalgia factor to make more work for themselves and risk angering a lot of fans? It just doesn’t make sound sense. It’s by far the most flimsy theory.

He was a powerful pony who became brainwashed by Chrysalis à la Shining Armor but much more extreme. We know Chrysalis has a penchant for attacking powerful stallions(King Orion, Emperor Incitatus) and it would explain his appearance and tie into her plan for revenge on Starlight Glimmer by reviving him.

Seems Grogar might become this alicorn instead of a goat. Wonder if Shadow Lock will be used in the main show.

Maybe Cosmos will be the S7 finale villain.

@Background Pony #CA36  
I mean the other person’s comments, something about lord mortuus

@immblueversion  
Maybe he’s like what I said in one of my previous comments?

@dynamicv  
Not likely. Much like Tirek and Scorpan, Grogar was a villain from the original 80s MLP cartoon, and he was a ram, not a pony. And much like how Tirek and Scorpan looked similar to how they did from the 80s, it’s a safe bet that Grogar could also look the same. Besides, his name doesn’t sound particularly “pony-esque” for this series.
 
@Background Pony #634D  
Also not likely, simply on the grounds that he doesn’t look bug-like at all.
 
If I had to place my bets, it will be a villain from an early draft of the upcoming MLP movie that was shot down by Sony in those Wikileaked emails. I’ll spare you the details, but the original story (which is much different from what we’re getting) dealt with an evil alicorn named Cosmos. And what does this drawing look like?

@thatguy  
I hope so

What if this guy is Grogar, and with his magic he inserted himself into the story of Gusty the Great?
 
Shadowlock said he can spread his own story into all kinds of books. And Twilight said that fear gives Grogar power, which would be a logical reason to spread through books. If enough ponies became aware, he would have the power to return.

Wonder if bringing this guy back will be in Chrysalis’ revenge plan

@Background Pony #634D  
Or maybe it’s not a changeling at all
 
Maybe this is something entirely different

Look like a king changeling to me. I wonder if this will has anything to do with Queen chrysalis revenge on starlight glimmer.

Kinda looks similar to an alicorn that I found evil
 
Lord Mortuus

@Background Pony #03DC
 
That’s a pretty solid guess, proto-changelings.
 
Those wings are quite…. unique, huh.

I’m betting it’s some creature we’ve never seen before. I’m no myth expert, but I don’t believe that’s a changeling (kinda looks like it). I could be wrong though.

@Poison Trail  
They already did  

Man, this reminds me of the Pony Creator days, anyone remembers those ugly filigree/metal wings?
 
Looks like someone at Hasbro does.

that not a changelings it something else.