Blue Demons

Black wings, bright blue eyes, nails that become blades, a power to kill anything in its path. It started with seven, but in the end there can only be one. At top of the food chain, they kill everything in their path. They cannot die, only be put to sleep. It started out a few centuries ago. They were going to be burned for being witches. They were only children. A deal was made and immortality was granted at the price of their souls.