Jabberwocks are big monsters, like a zombie hulk. Fast, hits hard, but normally you only see one of them at a time. I don’t think they even show up unless there’s a mission for it. In any case, have good melee and armor, or a good ranged unless you wanna get killed. They don’t have the smash attack of a hulk, but I think they can knock you on the ground.
Basically, you get coordinates on where to find them, and the coordinates are always in a forest. If you can’t see them, you’ll know a Jabberwock is there with the loud roar they do. Also, the ChestHole tileset can make things a bit dangerous, since their tiles on that tileset kinda makes them blend in with all the trees.
If you got the mission from the lab, you won’t have any coordinates to the Jabberwock.