Revenant

Revenant also known as avengers, are a race of undead creatures who exist only to exact their revenge on those who wronged them while they were alive. It is said that a revenant will wait thousands of years or more just to find the perfect chance to strike.

Creation
Revenants are a race of undead beings that have been described as a cross between a vampire and a zombie. The way a revenant is created is very similar to the way a Yōkai is created. However, they're not created from the emotions of others. Instead, they're born from the last emotion a human feels before they die. This emotion ultimately revives the human in the form of a revenant. Not any emotion will work because it has to be a strong desire for revenge. This desire is known as the Curse of Hatred (憎しみの呪い, Nikushimi no Noroi) and it is the source of all of a revenants abilities and weaknesses.

Physiology and Habits
Revenants physical appearance can differ from one revenant to another. Their physical appearances can range from monstrous and terrifying creatures to creatures that look like an innocent human child. Despite the very wide variety of physical appearance's most revenants look human or at least close to looking human.

Curse of Hatred
Revenants have the ability to give their Curse of Hatred a physical form. This red-colored predatory limb serves as a special weapon for revenants. The physical form that the Curse of Hatred has depends on the revenant to another. A couple of them have unique traits like being able to fire parts of it as projectiles. Regardless of its unique traits, this limb is very valuable because blacksmiths are willing to pay millions or even billions of jewels to just have one. This seemingly outrageous price is thanks to a group of special cells inside the limb. These cells give the predatory limb the ability to slay any creature, regardless of what the creature's strengths or weaknesses may be. Not even regeneration abilities work on the injuries inflicted by this limb, which allows the limb to inflict long lasting injuries on any creature. There is one major weakness to manifesting this limb. When the limb appears the cells within the organ slightly boosts the revenant's physical strength and nearly halts their ability to regenerate, making it a lot easier for opponents to severally injure the revenant.

Diet
The fangs and sharp teeth of a revenant makes it easy for them to eat the flesh of humans and their wrong doers as well as drink the blood of humans. These two sources of nutrition makes up a revenant's entire diet. The blood and flesh is a lot more than the only source of nutrition for a revenant. When a revenant eats the flesh of humans their Curse of Hatred uses the flesh to instantly replenish the body, giving their physical prowess a temporary boost. When they drink the blood of a human their Curse of Hatred uses the blood to give the revenant's Slayer Curse a temporary boost in power. According to myth, when a revenant feasts on the flesh of the being who wronged them they will experience a sensation that can only be described as absolute euphoria before dying.

Slayer Curse
While the Curses demons use is fueled by the negative emotions around them, a revenant's Curse is fueled by their Curse of Hatred. This has given the Curses revenants use the alias of: Slayer Curse. One major reason for this alias is because the type of Curse or Curses a revenant will be able to use depends solely on the weaknesses of the person they want revenge on. Like Slayer Magic, most revenants can consume other sources of their element or non-element. In addition, Slayer Curse gives the reveant a high resistance to the magic or Curses of the being who wronged them.

Physical Abilities
Most of a revenants physical abilities are considered top tier by human standards. The only exception is their supernatural strength, speed, endurance and regeneration.

Weaknesses
Currently, revenants only have two known weaknesses: Devil Slayer Magic and Shinigami Auxiliary Magic. These magics are able to kill a revenant because they are able to destroy the very thing that keeps them alive: their Curse of Hatred. How much exposure to Devil Slayer Magic and Shinigami Auxiliary Magic it takes to kill a revenant depends on the individual. The only other way to kill a revenant is to allow them to exact their revenge, completely destroying their Curse of Hatred instantly.

Trivia

 * Permission was granted by Per.
 * The idea to make this race came to me after watching a Culture Shock video about Undertale.
 * The Curse of Hatred ability was inspired by the Kagune ability from the Tokyo Ghoul series.
 * Interestingly, a revenant's eyes will begin to glow when they are in close proximity to the person who wronged them.
 * While both Revenants and Yōkai are born from emotions and gain their abilities from within the connection between the two species appears to be nonexistent.