Maybe I didn't understand the Wheel of the Rotapriests... but what happens when ix=0?
As far as I'm concerned, because the Rotapriest's Concordance starts as a roll of 1d4+1, as a key stat (so it goes from 2 to 5) and it cycles across that range endlessly, there is no legal input which would get you 0 when put to the i. If you somehow get to that result anyways, then how about: the Rotapriest hits a snag in the wheel, whose pressure is cosmically only resolved via the dissolution of the Rotapriest, who resets to 2 Concordance and gains 50 bad luck.
In terms of your confusion with how it works, that makes sense! Here is a blog post about the design ethos behind the Rotapriest, mainly about why it's written like that. Thank you for your interest!!
I understand to some extent what the page behind the link explains. I even know what the rule is supposed to create: an irregular, cyclic fluctuation of the value for Concordance, so that a Rotapriest has access to all four spokes of the wheel alternately. Nevertheless, I don't understand which game element the imaginary number “i” refers to. Is it not possible to give an example from a real game situation? That would make me happy.
I imagine i as the "Wheel" that the Rotapriests worship, and thus they put their Concordance to the Wheel and the result determines what powers they have. i, in terms of both literal game-mechanism and how a Rotapriest feels it, would be the axis that turns the wheel when the Rotapriest changes around it.