[major spoilers] GMs, what did you do with Sponsored by a Stranger background?

[HAximand]

I noticed the background "Sponsored by a Stranger" in the Player's Guide and one of my players has picked it. The background says the stranger asked "whether an insect hive mind could be manipulated at a distance," which obviously foreshadows the BBEG of the campaign.

However, after doing a Ctrl+F search of all 5 books, there's no reference to the background at any point. What did you choose to do with this background? Or what will you do, since I'm sure most people haven't gotten through the published books yet? Did you choose that the stranger is a specific person who comes up, or is it forever a mystery?

[keftiu]

It’s pretty clearly meant to be one of the Contemplatives, the brain-aliens that live on Akiton. With the King of Biting Ants menacing the planet, they have plenty of reasons to take interest in potential Magaambya students, hoping to point Jatembe’s successors at his oldest foe. The stuff about insects and hive minds refers to his Formian servants.

[Adraius]

Here's a reddit discussion about the Stranger in the SoT subreddit, which has a suggestion or two.