The 2014 Monsternomicon has a little sidebar on Grymkin:
"Grymkin are malevolent and devious supernatural creatures that visit mischief and violence on all those they encounter. The nature of grymkin is little understood and remains a topic of debate amongst extraordinary zoologists across western Immoren. These creatures are almost certainly not of the natural world, although their origins are as uncertain as their inscrutable motives. Some scholars believe they come from a realm beyond Caen, linking them to beings such as infernals; others consider them to be tangible manifestations of dreams and nightmares. All agree that they seem to visit suffering on intelligent creatures alone and rarely interfere with ordinary animals or beasts. All grymkin seem driven by perverse whims rather than ordinary predatory instincts. Some grymkin are believed to have specific vulnerabilities that circumvent their impressive supernatural capabilities. Some of these claimed disadvantages are incredibly esoteric, but others are quite common, such as the weakness of gremlins against feline predators. Regardless, grymkin have given rise to colorful folklore, though separating fact from fanciful exaggeration can be difficult. In many cases, the demonstrable facts are as outlandish and unlikely as the many stories that have been invented out of whole cloth."
One of the images we were shown was a dregg, a rank and file type, which aren't described as grymkin anywhere. The scarecrow is probably a grymkin. There's another shot of a hollow man, which has some people thinking undead. I think that's Flay, a grymkin living under Corvis with the dregg.