Beastiary : my own version

Fury

Furies, also known as Erinyes or children of Nemesis, are spiritual vengeance demi-demons in corporal form, these supernatural creatures are known to be vengeful but some of them prefer to call it justice or karma. They hold some form of self inflicted responsibility to kill those who hurt others but their vengeance can sometimes differ between furies depending on how they where wronged when they where humans. When a Fury shifts their pupils enlarge pass there irises but not the sclera, their lips and hair turn grey-ish black, they gain pale cold skin along with sharp powerful black claws and black paint like skin running down from the finger tips. Furies tend to be female but are not exclusive to being.

Becoming a fury:
Furies are born humans but can become vengeance demons when they are wronged greatly in life and are offered a deal by the mythological goddess "Nemesis" who is in fact a powerful demon from another world. She gives them a chance to take justice or vengeance by becoming part demon themselves. However if a fury has a child while currently being a fury they can start a fury bloodline causing the Fury species to grow in number in recent years however they are still fairly rare.

Vengeance:
Different furies have different forms of vengeance such as one fury had an abusive father when she was a young human so when she become a fury she inflicted vengeance on abusive parents while another fury found out his wife was cheating on him so when he became a fury he took vengeance on people who commit adultery.

Powers and abilities:
Furies have many supernatural abilities to help them claim vengeance.

Immortality: Furies don't age granting them the potential to live forever.
Superhuman strength: They have enough strength to over power humans and most other supernaturals.
Super endurance: They don't tire and can take a lot of physical harm without taking any real damage.
Superhuman healing: They can rapidly heal from most wounds and don't fall victim to diseases and poisons like humans.
Claws: They have black steel-like claws, which are described as sharp, short sword-like shadows. If you are scratched deep enough by one of these claws you will experience painful hallucinations causing temporary insanity which will slowly increase over time unless treated, the wound will burn black until cleansed by holy water, ultraviolet light or a purification spell. A Fury can also cure people of her claws effects if she wants or needs to however this is unlikely.
Empathy: They can sense the emotions of others and use them emotions to empower themselves in taking vengeance onto the wrong doers.
Teleportation: They can teleport to different locations to aid them in inflicting vengeance across the globe, when teleporting it is described as if they are fading away into the shadows.

Weaknesses;
Although being immortal demons of vengeance they still have weaknesses and can be killed.

Holy objects: Holy objects such as crosses or holy water will hurt but not kill a Fury as well as negate the effects of their claws.
Sacred ground: They can't step on holly ground such as churches , temples or places protected by witches without setting on fire or or being stop by an invisible wall.
Increased physical trauma: Though fairly indestructible they can be killed by a lot of damage to their physical form.