In Legion during the Rogue Orderhall campaign, you learn that the Broken Shore was a trap all along, the SI:7 knew this but were stopped by the Dreadlords before they could warn The Horde and Alliance.
Mathis was also replaced by the dreadlord Dethroc. You eventually save and free Mathis from this by the end of the campaign, but I’m starting to wonder if you really did.
You mean Mathias Shaw? I’ve mained alliance since I started playing in BC as well as having a maxed rogue since wrath and it still took me a full minute to figure out who you were talking about.
On topic, IIRC we killed Dethroc? Any particular reason you think Shaw is still a dreadlord?
While Dethroc was pretending to be Mathias, he took steps to urge Anduin to war. After Sargeras stabs the world and azerite shows ups, the SI:7 are the first to start poking around.
And it’s Mathias who gives Azerite straight to Anduin himself, which causes a rather odd reaction in Anduin.
Because they are spies. Seeing that the enemy is up to something and then finding out what that is is literally their job. Anything other than what they did would be incompetence and grounds for being fired.
Because Shaw is the head of SI:7; he reports directly to the king of Stormwind. I don’t remember Anduin having a weird reaction, but it’s been awhile now so I may have just forgotten that anything strange happened.
And who’s controlling that Dreadlord?
Another. Dreadlord. 
I thought it was Jaina that was the Dreadlord?
Also, speaking of Dreadlords. Man did i love how you could turn into a Dreadlord in the Legion pre-patch and kill everyone in the city. That was so fun.
Mathias: reveals they’re a dreadlord
Flynn: …jackpot
Naw. The one that’s really a dreadlord is Bain. The Bain that Rexxar went to save during the founding of Durotar is dead and he unknowingly brought back a dreadlord.
That old god attack on Highmountain and Thunderbluff during the Highmountain AR quest? Bain had a hand in that. Representing Garrosh, the orc that killed Cairne? Only a dreadlord would do that. Who was a major player in two Horde civil wars now? Bain.
Would’ve been revealed during the visions I suppose. 
So far, Shaw hasn’t held anything back which would mean it’s the true Shaw.
Flynn would.
The Scarlet Brotherhood is out here, spreading their flat Azeroth conspiracies again.
Daddylord
I think you’re all dreadlords.
Maybe I’m a dreadlord too.
Flynn told Matthias he liked tentacles in that one quest, but what we didn’t see was that he also mentioned being into size difference.
Dread lord or not… he’s just cringy.
Was it explained what happened to the Legion after Sargeras was… imprisoned or whatever?
…
/grin
This gives me ideas
Most of the Dreadlords are alive still, souls in the nether.
Some Dreadlords like Mal’ganis showed up on the Broken Shore then vanished all of Legion, presumably doing something else. Dreadlords have no loyalty to The Legion, we’ll see them again.
Because they’re evil? I thought all “demons” served the Burning Legion.
Because Dreadlords were an established society before The Legion, Sargeras found them on a planet corrupted by The Void, the one he carved in half.
Plus secrecy and deception are their main tools of trade.