The ravaged lands of Appalachia are rife with creatures of myth like the Mothman, the Flatwoods Monster, and the Snallygaster, all of which come from local tales of strange creatures appearing to UFO enthusiasts and other general weirdos in our own very real world.
Cited to be legendary-boss level spawns worth hunting down in their territories, these bad boys are rare to stumble across, but some dedicated hunting should lead you in the right direction. Hunting around the Mothman's very own museum is a good place to start for him, or turning on the giant lighthouse lamp. Moth loves lamp, after all.
Honestly, it's such a fun idea it's a surprise it hasn't been implemented before. Being able to actively take part in an online multiplayer as what amounts to be a cryptozoologist offers up all sorts of wild opportunities, with the creatures discovered so far able to bestow certain perks if they're treated nicely, or provide an intense battle if you unjustly laser rifle the majestic, wise old monsters between the eyes as you run past.