Where is Whispers of Doom?

After a long break, I’m going back and getting all the 10th Anniversary Achievements. But for the life of me I can’t work out how to start Whispers of Doom. I know I’ve played it before, but I can’t find it. I’ve played all the way through to All In and finished that, but it’s not showing up in my mission achives. What am I missing?

you have to sacrifice a goat to the sc2 gods to enable it.

You play it from the crystal in the lab of the Hyperion.
I don’t think it’s missable/tied to bonus objectives.

After “The Dig”, it is accessible from the Laboratory.
You may have to start a “New Game” from the beginning of the Campaign, unless you have a save before going to the final planet.