Board Thread:Episode Discussion/@comment-410526-20160130155211/@comment-25086632-20160131155329

That would make sense. Perhaps there are also other progenitor grimm out there (possibly on a scale from meh up to Dragon), they just continually leak black goo and whenever it gets somewhere with enough space the goo turns into a Grimm?

Idk, but the existince of this damn dragon opens up so many more possibilities.