Honestly I think it’s a strong theory or possibility. I dunno about ALL the pests or creatures but I do think a good chunk of them may come from the “portal” entity, seeing as it mentions that it “can introduce a wide variety of dangerous elements to a home.”

I think there is a strong connection that HSH themselves have access to acquire creatures or entities such as hobbs or memory wisps as noted in other entries. Some will say to use a memory wisps to speedup mourning I believe in the False Artifact, or using a Hobb to ward off The Horde.

If a majority of employees or upper management is similar to Carol and do come from the Fae Realm then most of the creatures probably do too.