Steampunk game in a kind of post-fantasy world, players run a small airship Firefly-style. They have a psychic encounter fairly early on with a kind of hive-mind community (the "Communion") that I style as a kind of massive unmoderated chat room. They basically trip over it as part of another mission, and get overwhelmed by the deluge of information; but each come away with a "gift" of knowledge they can use to learn specialist skills without spending time learning from a master.

Nobody has ever heard of this group, but they pick up a few long-term passengers who had the same experience, and want to work for passage up north to join Communion long-term. Aside from these passengers, they largely forget about Communion, except for a few times when a hostile power has tried to enter their minds - then they were able to freely spend points to buy additional mental defenses, which I described as an external force reaching out to cover them.

As they slowly wind their way north, they begin hearing bits and pieces about small towns at the northern border of the Empire falling to what the Imperial news calls "brass walkers" - things that were once people, but are now festooned with bizzare machinery. At one point they hear a firsthand account of a noble's manor falling to them - after some of the hired help unbarred the gates!

Eventually their passengers decide they've arrived, and the crew drops them off. The PCs also end up meeting a few members of Communion in-person, and the players immediately bond with them - it's essentially a psychically reinforced mutual aid society, which is catnip for my group. So when the local Communion community gets rounded up and disappeared for "insurrection", the PCs immediately set to work tracking them down and freeing them before they get shipped off - and before the Brass Walkers that have been spotted approaching reach the town!

They get their Big Hero moment, free their friends in the nick of time, slip past the Imperial Air Navy moving in to smash the Walkers, etc. It wasn't until later, when they were being interrogated by a third party, that it was pointed out to them - Walkers tend to move in force where Communion members are threatened. And a lot of the gear the party gadgeteer has been coming up with seems to use the same ideas as the Walkers' tech. One of the PCs was even remaking himself physically in a manner very reminiscent of Walker design! They don't call themselves Brass Walkers, of course - you always have to be mindful of Imperial propaganda! But some members of Communion do remake themselves physically more than others, just as my player is ..

TL;DR: Benevolent psychic hive mind that helped the players early on turned out to be steampunk Borg; revealed after one player took the first steps to self-assimilation!