CREATORS

Membership: Cygni, Sirius, Stygyro (and possibly thirteen (or more) others-see comments)

Purpose: Universal Domination.

Affiliations: In-Betweener; Doctor Stranger Yet, Visimajoris, Xander,
four unnamed agents

Enemies: Ancient One, Apalla, Clea, Dr. Strange, the stars (Grand Nebular mentioned)

Base of Operations: Creation II (a dimension accessed after passing through the Quadriverse)

First Appearance: Dr. Strange: Master of the Mystic Arts#19 (October, 1976)

Powers: The Creators each had advanced magical training and prowess, although the extent of the original abilities is unknown. Using power granted by the In-Betweener, they proved able to alter the nature of the universe. In the form of stars, they had virtually unlimited energy powers, including manipulation of heat, light, gravity, etc.

History: The Creators are a league of sorcerers from different time periods on Earth (ranging at least as far back as the Pre-Cataclymic Era). Their exact origins are unknown, but they gathered together with the goal of transforming themselves into stellar bodies, taking over the forms of the stars, and transforming the current/previous stars into human form.
The reason for this is that, at least in the Marvel Universe, the stars are the original source of all energy in the universe, including mystical. By taking over the power of stars, they would gain virtually unlimited power and be able to control the entire universe.
The Creators saw Dr. Strange as one of their strongest potential opponents.

(Dr. Strange II#27 (fb)) - The Creators became allied with the In-Betweener, who powered the creation of the Cosmic Wheel of Change. Using the Wheel, they began their plot to replace the stars. Stars they replaced could be identified as blue dots in the sky.

BTS-The Creators brought the being known as Xander to their realm, where they trained him in magic, and in other forms of combat.

(Dr. Strange II#19) - The Creators (and Xander) apparently manipulated the Ancient One, causing him to strip Dr. Strange of the title (and power) of Sorcerer Supreme.

(Dr. Strange II#20) - Xander attacked Dr. Strange and Clea. Although Strange defeated Xander, he did manage to cast a spell causing Clea to behave malevolently for some time. The Creators recalled Xander to Creation II.

(Dr. Strange II#22-BTS) - Clea rampaged through the city until Dr. Strange managed to remove the spell that Xander had placed on her.

(Dr. Strange II#23-BTS) - Dr. Strange journeyed into the Quadriverse to investigate the reason for Xander's attack. He attempted to save the "Guardian" of the Quadriverse from imprisonment, but learned that the nature of the realm was to have one Guardian imprisoned at all times. After freeing one, she/it was replaced by another.

(Dr. Strange II#24) - As Dr. Strange passed through the final portal into the realm of the Creators, they awakened Visimajoris to stop him. Strange was saved from Visimajoris by Apalla, who was a star that had taken humanoid form in an effort to stop the Creators' plot. Strange and Apalla confronted and battled the Creators, and Apalla located the Cosmic Wheel of Change. Strange was suffering from some type of malady that was making him act rashly, and he destroyed the Wheel, with the intention of stopping their plot. However, this did not stop them, but rather allowed them to rewrite reality as they saw fit. Without the Wheel, there was no way to reverse their changes.

(Dr. Strange II#25) - The Creators accomplished their goal, taking the forms of stars and casting the real stars into humanoid form. The now-humanoid stars were comatose after the transformation, and Strange placed them in stasis around the star which was once Alpha Centauri.