When Thanos died, his energy merged with Death’s, and as a result, the Rot was created, a moving void of nothingness. Rot started off as so tiny that Death didn't notice its presence. As Rot consumed more and more objects, it grew and grew. When Death finally noticed it, she realized the reason she couldn't detect its presence was that its nature was alien to her (it was an abstract being with no presence and was both alive and dead). Therefore, she held no sway over it.
Reptyl and Primo, sent by Thanos to capture Raptra and Quoi, received information from an informant that Raptra was heading toward the Rot. According to to their informant, the Rot just popped up one day and that going inside it was suicide, but it was good for hiding. Meanwhile, the Avengers also spotted the Rot. Mantis sensed that the Rot would eventually consumed and destroy the cosmic entity, Eternity. So, Vision and Mantis left to seek the Eternity's help, but Eternity informed them that he was powerless to stop the Rot. Elsewhere, Rot found Thanos' father Mentor and killed him.
When Vision and Mantis returned, the Rot swallowed them as well as Thanos, his minions, and his ship the Sanctuary. The Avengers later entered the Rot to battle Thanos and his minions to rescue Mantis and Vision. By now, the Rot had grown and that it was targeting all living things, as if it was sentient. Thanos attempted to flee via teleportation, but he discovered that he couldn't teleport and that Rot had completely encased him and the others.
Mantis made a force field to protect the Sanctuary from the Rot, but the Rot managed to break the bubble and instantly killed Primo with one touch. Mantis and Quoi then combined their power to make another force field, which managed to hold the Rot off. Thor, the Scarlet Witch, Reptyl, and Vision combined their power stop Rot, but Rot was completely unaffected by their attacks. Quoi also tried to stop the Rot, but none of his efforts were effective. After Quoi returned to the ship, Death suddenly appeared to reveal the Rot's origin. Death also came up with a plan to destroy Rot. Because Rot contained their combined essence, only Thanos and Death could stop it by going against their natures. They released their power with Death pushing and Thanos pulling until the Rot was dissolved, and all those killed by the Rot were restored.
Powers and Abilities
As its name suggests, the Rot has the power to destroy anything it touches. Whether it is matter or energy, anything that comes into contact with the rot will rot and disintegrate almost immediately. It is virtually indestructible as it cannot be destroyed by any physical energy attacks and it cannot be harmed or injured. It is of an enormous size of emptiness which continues to expand, taking up whole portions of space. Another of its abilities is that it is able to absorb energy directed against and add to itself. The Rot is considered both living and dead, since it is the offspring of Thanos and Death, meaning that nothing living or dead could effectively harm it. It has proven so powerful that neither Death nor even Eternity can affect it. Of everything the Rot is capable to destroy it has no apparent affect on inorganic matter, such as Thor's hammer.