I was referring specifically to the Nephlim and Woes. I could have been more specific, however. Ama No Zuko wandered into Malifaux from Earth. We don't know if the Oni originated on Earth as a species or if the went to Earth from Malifaux or elsewhere. From bits of fluff I've heard, Shenlong spent quite awhile on Earth before returning to Malifaux. It's possible that the Oni were created via magic of Malifaux. Regardless, the fluff did say that magic existed on Earth before the first opening of the breach, so anything is possible at this point, until explicitly stated by Wyrd.