The Entropy Cloud is far more than mere entropy bulldozing a universe. It is a rift in the very fabric in the space/time of Microspace bending past, present, and future together. This would be bad enough on its own were it not for the fact that the cloud itself seems sentient to a degree, reaching out to consume planets.
It has also been referred to as the Entropy Storm or (incorrectly) as a Chaos Storm. Which to be fair are much cooler names.
The Entropy Cloud came about when the Time Travelers attempted to enerchange with time itself. Micronauts #4 Wrath of Karza #1 All things within the cloud were held in a quantum state, both existing and not at the same time. Wrath of Karza #3 At the heart of the cloud rested a maddened Time Traveler. Wrath of Karza #5
One of the first planets to be consumed by the cloud was Sauria, wiping out the Reptos. Micronauts: Revolution
The cloud's destructive rampage through space caused the already quite large divide between the Ministry of Science and the Ministry of War to descend into full scale civil war. As a result of the cloud, many citizens believed the end of all things had come and began taking bets on which worlds would die first. Despite the war, the Ministry of Science sent a squad of Biotrons to Saqqura to observe the world being destroyed by the cloud. The squad noticed that the cloud's tendrils were reaching out for Saqqura with signs of intelligence. Though the scientists understandably wanted to evacuate, the Biotrons insisted on staying to be destroyed with the planet so their final moments could be recorded and sent to the Ministry for further analysis. Micronauts #1
The cloud would occasionally eject debris. When Baron Karza was brought his own helmet, though heavily weathered with age, Micronauts #4 he began to speculate that the cloud was in fact a rift in time. Baron Karza's profile
After Karza's attempt to steal weapons from the Valtricos Research Station was foiled by some ne'er-do-wells, Micronauts #3 he launched an attack to capture them after learning they had a Pharoid among their number. Micronauts #5 After an out of body experience with a Time Traveler, Oziron Rael directed his crew to fly their ship into the cloud. Glimpsing their escape, Baron Karza followed them into the cloud. Micronauts #6
The cloud however bent time and Karza arrived inside years before his quarry. Baron Karza's profile The Baron took this opportunity to study the cloud and at the very heart of the cloud discovered the inert body of Micronus Prime, who he soon determined was the creator of Microspace. Learning that his creator came from a different universe, Karza studied the Prime's personal Spacebridge and through it was able to make contact with the other reality and discover Ore-13, which could halt the cloud's effects. The Micronauts (only a few days having passed from their perspective) reunited with Karza when they tracked down the energy emanations from Micronus's spark. Micronauts: Revolution
Though Karza had made an attempt to use Dire Wraith magic to bring the Ore-13 into Microspace, he was ultimately defeated and forced back to his realm. Valley Forge He stewed for a year as he watched the cloud devour more of Microspace until Shazraella convinced him to abandon Microspace to the cloud and start anew on Earth. Wrath of Karza #1 While on Earth, Karza revealed to her the nature of the cloud and how it could not be destroyed without negating Microspace's existence. Wrath of Karza #3 When Shazraella unleashed Time Traveler energy on both the Micronauts and the Autobots, she lost control of her power and threatened to unleash the Entropy Cloud on Earth forcing Optimus Prime and Baron Karza to ally and stop her. She proved too powerful, however, and was only defeated after Oziron Rael had ascended to become a Time Traveler, whereupon he and his new brothers tore the Mad Time Traveler from Shazraella and halting the Cloud's Earthly rampage. The Time Travelers then pledged to Optimus that they would repair all the damage the Entropy Cloud had caused, starting with the damage caused to Earth. Wrath of Karza #5
Months later however, the Cloud was still active and projected to consume all of Microspace in slightly over an Earth year. Discovering information about the Presence, Baron Karza sought to end the Cloud's threat by forging an alliance with the Dire Wraiths, ROM: First Strike Microspace Knight wherein the Cloud would be funnelled to the Presence's dimension and accelerate her own growth while ridding Microspace of the threat. Microspace Knight
After Karza had enerchanged with Rom, the Knight materialized in Microspace within the Entropy Cloud. Small World The Micronauts followed to rescue their friend where the group soon managed to deduce the villains' plan. Following the signal of the Wraiths, they found the Cloud being funnelled out of Microspace via an asteroid. Microspace Knight Rom managed to destroy the conduit the villains were using setting the Entropy Cloud back to its normal chaotic state. Entropy
In the timeline from which the Sentient Time Chamber hailed from, the Entropy Cloud consumed everything in Microspace, the last system being Udunax. The Chamber used his powers to shield himself and a handful of Kronus from total event collapse before they drifted within the Entropy Cloud for thousands of years. Micronauts #9
- Entropy Cloud at the TFWiki