Old Ones
The Old Ones are a group of utterly inimical Beings that seem to have little relationship to the natural order of things.
Near them, the laws of Nature and Magic become warped and hostile to anything nearby, which are often twisted to accommodate this outre existence.
They often enter or leave Mundus during Autumnset, when paths to The Shadowfell lie open.
Other races also arrive via The Shadowfell.