Can I get an example of this, for plot hook purposes?
Trying to calibrate the possibilities.
A group of Modrons enters a small village. Once there, they sing a song, or activate an object that plays music. The people of the village are compelled by -absolute order- to begin the construction of a machine alongside the Modrons, including using several modrons (broken down into component parts) to incorporate into the machine. This machine requires metal. And once it's reached a certain size, just pressing metal against it is enough for it to incorporate metal into itself.
The majority of the Modrons leave. A handful remain as overseers of the Machine. The villagers sacrifice all their metal to the machine. ALL OF IT. And begin hunting passers by for more metal. Eventually they start sacrificing each other to the machine. Tearing out gold teeth to feed it, making offerings of blood, which contains iron and seems to "Appease" the Divine Machine.
And that's when things start going off the rails.
The Modrons oversee the Machine's continued construction. Uncaring at the cost of lives that are being cast into the machine. It is -required- for the Great Ordering. It must be protected and continue to construct itself. If asked why they're doing this, the answer is simple:
"This is Required. The Great Ordering must continue. The Machine is a part of that Order. Give us your metal. Add it to the Machine."
And then have a fight sequence where the villagers -help- the Modrons and do their best to drag the player characters over to the Machine. Have an NPC hireling or something wearing metal armor get pressed against the Machine... and pressed out of their collapsing armor like a handful of ground beef squeezed in a fist.
"It is Required."
