The Defenders may have been one of the strangest "non-teams" to hit the pages of comics, but they had some competition in that category with a ladies' auxiliary team that came together in a Fantastic Four story where the Invisible Girl had fallen into dire peril! And fall she did:
Memory escapes me just why Tigra and Thundra were hanging with the FF--probably something to do with their mutual crush on Ben Grimm. As for the Impossible Man, he'd been around for a few issues because of his preoccupation with fun--and who's more fun than the FF? While the Baxter Building isn't exactly the most uneventful building in Manhattan, it's still not every day you see one of the FF being hurled through a window 35 stories above the street. And it's a good thing the Impossible Man is close at hand in this situation, because he's about to be introduced to the "fastball special":
As to what's been going on in the Baxter Building, the Counter-Earth version of Reed Richards has been posing as the real McCoy after he'd brutally hurled the real Reed into the Negative Zone and subsequently took his place in both the FF and as Sue's husband--"brutally" being a reference to CE-Reed in fact being the mega-strong and ruthless Brute, a purple-hued creature whose encounter with cosmic rays on his world resulted in a very different transformation.
With the Brute having trapped the rest of the FF in the Negative Zone as well, it's up to Sue to deal with the Brute (even though we can probably call a 35-story plunge "Strike One" in that regard)--and with her "sisters" at her side, a new team is born! A team that could certainly use the Impossible Man, going up against the Brute--but without the prospect of fun, it looks like the ladies are on their own.
I have no idea why the FF bother to have a secure, private elevator that's locked to the general public, yet leave stairwell passage available to anyone who wants to make the trek up to their residence. It's still nice to see Sue acting so assertive and taking the lead in this operation, which only makes sense since she's familiar with the layout of the top floors and their defenses.
And just look at her go here--thinking on her feet and showing Tigra and Thundra what teamwork is all about!
Meanwhile, the mad Thinker has entered the picture, recalling from the Negative Zone his deadly, multi-powered android. The Brute would normally be powerful enough to challenge it--but the android has also absconded with the cosmic control rod owned by Annihilus (jeez, this story is throwing in everything but the kitchen sink!), and its power is uniquely suited to counter the Brute.
With the Brute out of the fight, the android poses a new threat for our ladies. (Just what do we call our new team, anyway? I say we recycle the name used by the all-female S.H.I.E.L.D. strike force that briefly appeared in '72--the Femme Force!) Unfortunately, even with Thundra on the team, the android's power is overwhelming--so you may not want to expect a charter from this new team anytime soon.
Fortunately, the rest of the FF make it back from the Negative Zone in the nick of time--and acting together, everyone coordinates under Reed's direction to finally disable it.
As for the Femme Force, they're fated to become a one-hit wonder. Sue becomes... well, Sue again, tending to Reed and basically falling to pieces until he recovers from his ordeal. As for the others, a rift forms between Thundra and Tigra over the attentions of the Thing, and that's that for any future appearances of these three.
(More like a cold war, since nothing comes of the harsh words exchanged between them.)
Looks like this story's title is also a product of recycling, with Thundra bringing us full circle!