We’ll never know most likely, since we’re already lugging around five of the damn things and my mc absolutely does not want to go for number six, no matter how compatible. Or at least not without getting rid of the other five first.
My purely speculative fan-theory based on nothing more than the incompatible ones calling the mc “beloved of Isha” is that it would have been Isha herself. But since the mc can only call upon their phantasma including the newest one for a couple of agonisingly painful seconds at most there is no way to question them, assuming they’d even answer real questions.
But that is just my fan theory. In-universe my mc doesn’t know and quite frankly doesn’t much care either as his priority is trying to get rid of the parasites, not adding yet another one to the mix.
Yep, the whole “let’s not teach our own kids the knowledge they actually need” was likely terminally stupid as it was certain to guarantee stagnation and decline instead of innovation and prosperity. Imagine if we’d force our kids to reinvent electricity every generation.