What will happen if the wights take control of the loops?

From the text:

“If what the animals say is true, and all our ymbrynes have been kidnapped, soon even this won’t be here.” She gathered
some dirt in her hand and scattered it in the breeze. “Without ymbrynes to maintain them, our loops will collapse. The wights will use the ymbrynes to re-create their damned experiment and it’ll be 1908 all over again—and either they’ll fail and turn all creation into a smoking crater, or they’ll succeed and make themselves immortal, and we’ll be ruled by those monsters."