It's a big coincidence to find that thread. I've been thinking about what Gehl Bulfs are, too. This is what I came up with myself, it's not official, but I liked the detective work to put this down to words:
Gehl Bulf: Areas saturated with negative photon activity can result in a Falspawn phenomenon known as Gehl Bulfs. Resulting from the constructive interference among the wave functions of negative photons, they form the same way as ocean rogue waves do during a storm. Because of the F-Factor, after condensing in its mature form, it will chase down living creatures. It won’t last long, but can cause enormous damage while active. Because a Gehl Bulf has no material body and is barely visible to normal vision, the only thing to do is to run. To this day, only high density photon wallops are known able to negate a Gehl Bulf, and are provided only by heavier caliber weapons such as the ARKS Photon Cannon.
If you've been through this already, there's the revealed "storm of negative photons", and possibly many Gehl Bulfs arising from it: