[Enchilada645]

Yeah it really is weird, they honestly just seem to be in and out when it comes to like, their presence.

Cause W through Fourze, there was this building and them being dealt with. Then they went silent for a long while until Ex-Aid I believe with the Beast Rider Special. With them studying the Bugster stuff which leads into the whole Enigma Incident of Heisei Generations Final.

Edit: Mid post edit but I do recall that the villain and helper fairies of Battride War were like former Foundation X people too, and that came out during Wizard. Not the most but hey it's there. lol

After that they were mostly gone and then they pop up again in video game form via Memory of Heroez. But yeah they're fairly sporadic and it just seems to be up to whoever is writing at the time to push for them really.