The other dimension, what is it?

Pap is the reason Ludi is full of monsters. It's not clear how the "Dimensional Schism" came about, though. Part of the Time Leap quest said something about how pap came to Ludibrium. I don't really remember it, though. Versal might be a different dimension from the one that's part of Ludi's story line, as are the 3rd job portals different dimensions from the others.

it says he used a crack in the dimension to travel through time.