The Celestials, creators of both the Eternals and the Deviants on Earth, later created the Brethren. The Brethren were formed not from humanoid forms like the previous creations, but instead from bacterial life from the planet Omega Climion Six. The Brethren were used as a weapon of Arishem the Judge, who would determine if a planets life forms were worthy. If Arishem found them unworthy, he would send the Brethren in to eradicate all life on the planet. For an unknown reason the Celestials eventually left the Brethren to wander the Universe, but they were eventually found and captured by the Collector.
Notable members of the Brethren are Thane Ector, Sybyl Dorn, Fool, and Olar. The leader of the Brethren takes the title Thane, and he is to have two sons. The two sons are told on their 15th birthday the true origins of their race. With this revelation one brother would be named Thane, while the other would be driven mad by the truth. The leader of the Brethen in their encounter with the Inhumans and Avengers was Ector.
The Brethren are sent to Earth by the Collector and encounter the Inhumans and Avengers, and they attempt to wipe out the human race from Earth. Eventually thanks to Sersi and the Avengers the Brethren are able to escape the Collector’s control and fight against him. This did however lead to the end of the Brethren race as far as we know. It is not known if there are other surviving members, but due to their hive mind, it is thought they all perished when forming the Uni-Mind.
The Brethren are a Marvel comic book team and were created by Bob Harras Tom Palmer and Andy Kubert, and first appeared in Avengers Vol 1 #334.
Major Story Arcs
The Elder of the Universe, The Collector, decides to use the celestial created alien race, the Brethren, to eliminate mankind. Capturing them, then allowing them to escape, rather manipulated into being put on a course to bring them directly into contact with Earth. The Brethren crash land near the Blue Area of the Moon, and this brings them into direct conflict with the both the Inhumans of the Moon and Earths mightiest heroes the Avengers. Brethren attacks were on a world wide scale, and clashes between the alien invaders and Avengers were held in both Paris and New York. Thane even took over the World Trade Center as his citadel.
Powers and Abilities
The Brethen's true form is shapeless, and they have displayed shape-shifting capabilities. Though not all Brethren display more powers, many of them do have enhanced powers. Thane Ector displayed super strength on par with many Avengers, and the ability to produce energy beams from his eyes. He also looked to be able to fly, though it is not known to what extent. Sybol Dorn, Thane's second in command and betrothed, also had super strength and the ability to produce energy beams from her eyes. Olar was extremely skilled as a shape-shift. Fool, Thane's brother, was a telepath.
The Brethren share a hive mind, and were able to form the Uni-Mind in order to defeat the Collecter, and displayed some abilities akin to the Eternals, allowing them to clear entire planets quickly.