Darkness

Darkness appears in the Chronicles and the Saga with the same message, "Darkness is coming". Not much is known except that another person which Darkness mother is mention appears, she too is a mystery. Darkness is black wing so she could be connected to Dark. Unlike Dark she has 4 wings not 2 which might suggest that Darkness is stronger.

Power
Not much is known about her power, she might be connected with Dark's power.