You might be thinking of this, from Blizzcon 2019:
https://www.wowhead.com/news=296023/the-jailer-is-the-main-villain-of-shadowlands-working-with-sylvanas-since-edge-o
Q: Did the jailer in The Maw see the Legion as a threat which is why Sylvanas worked with Varian?
A: We’ll find out more of her motivations in Shadowlands and that her relationship with the Jailer dates back a bit. Edge of Night story involves this relationship. Working with Varian was a long term strategy in order to get Warchief - had to make allies but now we’re seeing the fruition of that.