The Darkness: “YoU aRE NothInG BuT mY puPpET!”

Nice theory

@Background Pony #8A97
 

 
Um… that never happened in the show?
 
Did you mean Grogar? Because that’s more of an intimidation case, as with the other two.

@Background Pony #8A97  
I’d imagine Tirek and Chrysalis have no relation to the Shadow, true. But their fear explains it, just look over their responses, they are deeply intimidated by Grogar.
 
Yes, Grogar and Sombra are more “pure evil” than their greed-focused desires, but the thing is that they can’t just refuse to work with them: Refuse to work with Grogar and you’re probably dead. Work with him and he’ll keep you around at least for a little while, while you plan a way to survive when you inevitably fulfil your purpose.

@Background Pony #8A97  
When did they?

This heavily implies that Queen Chrysalis would never have anything to do with them.  
It’s already a popular criticism: why were Sombra and Chrysalis cooperating?

@Dustcan  
There isn’t enough time left in the series to fully reveal it, unless maybe it is blatantly stated by Grogar at the series finale.

Would be cool if there is an over-arching threat with all this. But I think it’s just fluff.

@pwingbrony  
The common personality traits really give away that there’s some form of possession going on in a lot of cases. If it cackles maniacally, you’re probably dealing with Shade.

Not a bad theory. Could explain a number of other enemies and beasts too.