Council of Thieves
Shadow Beasts are insectoid creatures with tendrils of shadow power flowing from them. They can use their shadows to make stingers, or gliding wings. They can jump and some can even teleport. While small and easy to kill, their stingers do as much damage as a Great Axe or 2 Handed Sword.
Shadow Beasts come from the Elemental Plane of Shadow through portals that exist in seemingly random places where there are no lights. These portals seem to be “weaknesses” in the barrier between realms. Each portal seems to generate two shadow beasts before closing on its own.
There is also a Shadow King, a mass of shadow beasts that is larger and more powerful than the smaller ones.