The Red Angel

Yes.

So for context for the listeners at home, this takes place in the early middle, late beginning of season two of Star Trek Discovery in the middle of the Red Angel arc after we've been Spock teased and yet Spock blocked for five episodes in a row where he's still not there.

I remember that being an overriding sensation.

Like, oh yeah, great story.

Actually, I should say Saru uses the Ba'ul's technology to trigger Vahari in all Kelpians, hoping the two species can instead work towards a peaceful solution once the Kelpians

are freed.

The Ba'ul retaliate against Starfleet's action by attempting genocide on the Kelpians, but are stopped by the Red Angel, whom Saru sees as a humanoid wearing a highly advanced suit.

Yeah, and thanks to Memory Alpha for that synopsis.