Where can I find the details of the Legion of Folded Paper Feat?

I’ve been tooling around with a Pathfinder 1E campaign of mine, specifically with trying out some templates for potential monster encounters. While I was doing this, I stumbled across the Ofuda template. It puts some interesting restrictions on the creatures in question, but what caught my eye was the bonus casters get for summoning Ofuda-ized creatures over the standard types. You get to summon additional creatures than the spell normally would, 1d3 instead of a single, 1d4 instead of 1d3 and I assume 1d6+1 instead of 1d4+1. However, it mentions a feat by the name of Legion of Folded Paper that would increase the number of bonus creatures you’d get from a single cast. The problem is I can’t find this feat anywhere online let alone the specifics for how it works.

Does anyone know where I can find these rules? Does anyone know how this feat functions?