Karma

Karma (カルマ, Karuma) is a non-standard Servant Class containing beings brought forth due to direct consequences of using the Holy Grail, or any other wish-granting device. Due to the very nature of the Holy Grail Wars before their abrupt end, it is unbeknownst to the participants that these beings existed until they brought forth the end of humanity. As a result of this, the respective timeline in which they formed within was exterminated by their own hands, causing them to travel between other timelines. Their very existence, regardless of their affiliation, has been deemed a Threat to Humanity.

The Karma are major antagonists within Fate/Advent.

Overview
Everyone and everything has a wish they wish to fulfill, whether they make it known to the world, or it remains unspoken until their untimely death. The Holy Grail is but one of the many possibilities to achieve any and all wishes. However, each wish, once granted, requires certain criteria. These criteria can be summarized as karma. Regardless of the wish, whether it is deemed good or bad for the world, they all fall under the concept of karma. Over-usage of these items that can cast wishes bring about the manifestation of humanity's karma. Befitting their name, the Karma are pre-existing beings that were, in essence, summoned by the wish-granting device used. However, there have been those that erroneously hypothesized that the Karma are subservient to the wish-granting device that brought them forth, making it similar to a Master and Servant scenario. In truth, the wish-granting device acts similarly to a beacon that allowed for the Karma to be summoned to that timeline without restriction. The most common reason that a Karma offers as to why they were summoned is simply because their own Domain (ドメイン, Domein) was trespassed upon without their given consent.

However, trespassing on a Domain requires for the Karma in question to own it, usually referring to a Divine Spirit. While this would normally be correct, for those that would be unable to be classified as a Divine Spirit, the wish plays a major part in their summoning. After the wish-granting device takes away from the world to bring about its user's wish, a Karma may form shortly afterward, unbeknownst to the wisher. Due to this summoning process, a Karma is basically deemed the embodiment of the wish they came from, such as in the case of Avenger, who became a Karma after abusing the Wish-Granting Pearl, and it becoming one with him, using it to create a "perfect China", thus making him the Karma of China.

The mere existence of a Karma, as stated prior, is a major Threat to Humanity. However, due to how they are summoned, some can deem the Karma Saviors of Humanity (人類の救い主, Jinrui no Sukuinushi). Where the World has failed in maintaining itself and its residents, the Karma exist simply because of the World's own incompetent actions. It creates defense mechanisms, such as the Counter Guardians, to try and protect itself, but humans, and subsequently certain Servants, continue to do as they please. It is due to these actions that the World has came close to being destroyed across the present timelines. In allowing its residents the chances to abuse near omnipotent wish-granting devices, the World has forsaken its right to fully govern itself. All wishes, regardless of their purity, lead to all wish-granting devices making grievous choices to make said wish happen. However, even devices of the World grow weary of being used. In essence, the Karma can be the Saviors of Humanity, where humanity itself is a Threat to Humanity.