Origin

About a hundred thousand years ago, the Skrull, at that time a peaceful race of traders, roamed the universe in search of civilizations to trade and share their technology with. At some point, they discovered the planet Hala in the Pama star system. This planet was inhabited by the telepathic Cotati, who had evolved twenty million years ago, and the more aggressive Kree. The Skrull gave both races the task to create a habitable area on Earth’s Moon, to determine which race was worthy of the Skrull Empire´s advanced technology. 
 

The Kree built a huge city, including artificial gravity and self-replenishing air, to come as close to the circumstances of Earth as possible. This habitat was going to be known as the Blue Area of the Moon.
But at last, it were the Cotati that won. They had developed an enclosed ecological system for the area, which was mandatory for its habitation.This inferior treatment enraged the Kree so much, that they killed the Skrull ambassador and his crew and took advantage of their starships technology.
That started the eon-long Kree-Skrull War, that involved many races throughout the universe.

But the Kree were so furious, that they not only slew the Skrulls, but also diminished the entire Cotati population. Fortunately for their races survival, they were able to spawn a new generation before dying. Their survival instict also led to a devolution of the Cotati. They started to transform into plain looking plants in order to hide from the Kree, while perfecting their mental powers. They were cared for by the Priests of Pama, a sect consisting of peaceful Kree. In return, the Priests were taught the secrets of the mind.
 
The Cotati spread unto many living worlds, after the Supreme Intelligence forced the Priests to flee by . At last, they came to the planet Tamal, which became the plantpeoples refugee. They also landed on the planet Earth, where the Cotati meant to fulfill one of their own prophecies. A prophecy that foresaw the union of the perfect human with the perfect plant, the result of that being the perfect child, the Celestial Messiah, "the most important being in the universe".

The fleeing Gustav Brandt sought refugee with the Priests, accompanied by his infant daughter, who later came to be known as Mantis. They trained Brandt (later to be known as Libra), but separated him from his daughter to train her without his violent influence. They believed her to be one of the candidates to become the Celestial Madonna, future mother to the Celestial Messiah; another candidate being Moondragon. They trained her in martial arts originating from the Kree Empire, thereby honing control over her physiology. As an adult, her memories were erased and she was sent out into the world to gain experiences.

In a fight between the Avengers and Zodiac, the defeated Libra filled Mantis in on her missing past. Then they visited the Priests temple, where Mantis found the eldest Cotati to have inhabited the resurrected body of the Swordsman, whom Mantis had fallen for before his death. She came to terms with her destiny as the Celestial Madonna and married the eldest Cotati in a double-marriage together with the  Vision and the Scarlet Witch, which was officiated by Immortus.
 

After the ceremony, Mantis and the Cotati transformed into energy and left Earth to mate. After giving birth to Sequoia, Mantis tried to raise him in the town of Willimantic, Connecticut to give him a background as normal as possible. But at one point, the High Cotati, the council of the Cotati, felt that Quoi should be raised by them. Not agreeing with the Cotati, Mantis, aided by the Silver Surfer and the Fantastic Four, fought the plantpeople, who got help of the Priests of Pama and Kang. When the Cotati realized, that they couldn’t win this fight, they fled, taking Quoi with them.

Accompanied by the Avengers, Mantis found her son on Tamal, who needed protection from Thanos. Obviously, most of the Cotati, including the Elder Cotati, didn’t share their council’s opinion, since they came to welcome the newcomers. But upon failing to protect the Celestial Messiah, the Cotati attacked the Avengers, who barely managed to escape.
   

Powers

Though once human, the Cotati have given up their mobility for constant meditation. They have incredible mental powers linking them to all plant life in the universe. They were able to easily defeat the Contemplator, one of the greatest minds in the universe.