After the Underworld Master constructed the Megachest to seal Megadon and Chester away, it is buried far into the ground in hopes that no one ever finds the chest. However, a few centuries later, an old civilization of hunters found the chest and opened it, which exploded one of the hunters and turned the others into dust. A bystander watching the incident records the catastrophe of the opening onto a papyrus plant, which doesn't get found for a long time... until Harry Huber finds the papyrus plant at a beach, causing him to eventually find the chest and open up the Huber Archives to show it at display. The chest was only guarded by tempered glass, causing the next opening indirectly.

Many years after the Megachest was put at display, a group of AOE members figure out the true power of the chest and eventually commit a heist on the museum, stealing the chest. Bimmy, who at the time is not extremely popular, must defeat the AOE himself since his older brother, Timmy, is on vacation at the Bahamas. Bimmy eventually gets captured and is forced to witness them opening the chest, but it instead turns on the AOE and explodes all of the members involved in the opening. Bimmy survives by hiding behind some debris, and the chest is then sent back to the Huber Archives, now stashed away on a high floor covered in layers of Basitine.

Azazel Odium, also known as Mugore, gets invaded by Swiftmen due to suspicions of him working on Project EROS. Bonico travels to Tokyo, Japan at an AOE base to uncover secrets about Project EROS due to strange signals from the building. Bonico gets attacked by AOE, and Mugore surprise attacks him, but then mysteriously vanishes. Bonico then comes up with the deadly plan to hijack the Megachest, causing the Swiftmen to search and try to assassinate Bonico. However, the chest is opened and Mugore is flipped inside; Project EROS is eventually defeated, causing the Swiftmen to spare Bonico due to his good intentions and wise yet risky planning.

This takes place shortly after Project EROS. The MegaChest was currently in the hands of the high-ranking crime-lord Salazar in Antarctica.  After the failure of EROS, the INT demands all of their investments into the AOE to be returned. When the AOE refuses, the INT kidnaps hundreds of members of the AOE's 809th division. The 809th division, at the time, was the largest AOE division. The INT planned to execute them secretly in Antarctica where no laws existed. Salazar, the leader of Antarctica, had several AOE divisions guarding his palace so he lended the MegaChest to the AOE to be opened on the INT convoy's path. Salazar's personal AOE crew helped save several members of the 809th division and a lot of INT members died.

After trying to evade a massive top-secret bunker to obtain large samples of chemicals A and B, the AOE resort to using the powerful Megachest. Learning their lesson from Zingzling, they notice that opening it themselves would result in certain doom. Unfortunately, a random kid happened to be walking nearby while the AOE were discussing the matter, so an AOE goon sneaks up on them and tells the kid that the Megachest is filled with lots of toys. However, as the kid opened the chest, they leaned a bit too far forward and slipped into the chest, even shaking the mere AOE goons as they witnessed the brutal death. The kid got a game deletion.

To destroy everything, Dark Luminant resorts to opening the Megachest, as Bonico always stops his plans. Lance and the Dragon Master even join in. Dark Luminant explodes, Lance gets pinned by thousands of swords, and the Dragon Master freezes, meeting an ironic doom as he helped create the MegaChest. However, Dark Luminant still ends up returning due to him converting into what's left of his body after the blast into pure darkness and hiding in the shadow of the chest, which the dragons were unable to find and destroy, consequently securing Dark Luminant's respawn and reign of terror due to him dying a normal death of bleeding darkness, not a brutal shredding.

During the climax of the Last Soul, the Megachest is opened to spice things up in the competition. Many people were eliminated as a result. This was one of the many magical items used to spice up the competition during The Last Soul.

Occurring in the Eginoulo era, Harry Huber, infected by Chemical Z (Zenith), opens the chest and infects the dragons within, bringing them under the influence of Chemical Z. Megadon devours Chester into dust, turning into a malformed, bulk dragon with a gross, darkened orange color. With Gross Megadon's heightened power, it shatters the chest, and the Underworld Master is left with no choice but to brutally exterminate Gross Megadon by ripping it in half. The Underworld Master had enough power to resurrect the chest, but it was rendered useless because of the absence of the dragons.