Crimson Sovereign

The Crimson Sovereigns (赤元首, "Akagenshu") are a race of beings which inhabit the spiritual dimensions. Unlike the other beings inhabiting the worlds, Crimson Sovereigns are nature spirits of such great powers that even normal spiritual beings can't perceive them. Because they are also part of nature, they can use their power to change the world around them as much as they want. The Master-Class Crimson Sovereigns can be classified as a type of large; however, most of the Master-Class Crimson Sovereigns these days have had their true potential sealed off. As of now, only thirty full-blooded Crimson Sovereigns roam the spiritual realms, due to most of them being sealed in Akasekai, their home dimension.

Origin
"Well you see, the Crimson Sovereigns didn't originally exist in this world. The arrival of the Rockshatter comet and me, and finally the creation of this dimension into the universe, resulted in life-force sprouting forth."

- Tsukasa Tsugami, A Fate Sealed

Inherant Skills
Inherent Skill ( 先天固有技能(インヒューレントスキル)  , inhyūrentosukiru, shortened to IS) is the personal skill is a specialization of each Crimson Sovereign, ranging from passive abilities, e.g. Yuuki's Innate Time Control, to purely combat applications, e.g. Zakura's Luminokinesis. Although the IS may appear like a spiritual technique, it is not, as it cannot be learned or otherwise directly transferred to anyone but its owner because it is intricately tied to a particular Crimson Sovereign's soul. More often than not, the IS embodies a particular aspect of the Crimson Sovereign or what they strive for. If the Crimson Sovereign was reincarnated, then the IS will represent a skill which they have once possessed.

Master and Servant
Master-Class Crimson Sovereigns can infuse other races with their blood, reincarnating other beings into Crimson Sovereigns. From there on, the reincarnated beings are labelled as "servants" to the Master-Classes; essentially being familiars of a sort. In order to survive, those reincarnated must drink the blood of their "masters", transferring energy through exchange of bodily fluids, such as another drinking their blood, but it is strongest in the act of intercourse. It is required for "servants" to drink the blood of Master-Class Crimson Sovereigns three times a week; and if separated from their master, then they will begin to rot away before dissolving. In the cases of several masters and "servants", their relationships blossom into that of deep romantic love due to their connection.