Mazoku Slayers
Flare Dragon Cepheid & Ruby Eye Shabranigdu battling.

Name: Mazoku / Shinzoku
Origin: Slayers
Classification: Mazoku / Shinzoku, Magical races, Mystical Race
Age: Ageless, they don't age
Population: Unknown but countless fodder lesser and brass demons / 5 members of the Shinzoku (just in the Slayers Stave)
K - Level: Level 3 to Level 5 (Darkstar could eat all the energy of a universe)
Technology: Depending on the assuming form and time frame it ranges from medieval to intergalactic, creation of parallel universes, assimilation of technology, etc.
Powers and Abilities: Energy manipulation, dimensional manipulation, flight & levitation, illusion creation (can project an image of themselves which can interact with the physical world as if it was real), non-corporeal, teleportation, shapeshifting, reality warping (from low to high level), regeneration.
Weaknesses: Nothing notable
Industrial Capacity: No applicable
Holdings: Depending the Stave, universes or fractions of it. (they generally work in the shadows).

CIS: These races, especially the Mazoku, are held by a strict code of conduct in which they can't use most of their power against anything they deem as food or not an enemy (humans). One of the rules is that they need to be in the material plane (with an illusion) while fighting a human so they can be spotted.

Spellcasting: Mazoku can freely use shamanic magic but no dark magic, as calling the power of another Mazoku is like saying "I am not powerful enough" and this damages their ego and themselves.

Notes: Mazoku feed and gain more power when there are "negative" emotions while Shinzoku do the same with "positive" emotions.