Mollusc Era

""With creatures of the surface driven to extinction by rising sea levels, the ancestors of Inklings were free to haul their 10-legged bodies up onto the abandoned land. This is how the Mollusc Era began.""

- Sunken Scroll 10

The Mollusc Era is the current time period in the Splatoon series - M.E (Mollusc Era) is used as a year label, such as A.D (Anno Domini), and B.C (before Christ). It began roughly 2,000 years before the events of the games and 10,000 years after the earth flooded, causing the extinction of all land mammals (with the exception of Judd and Li'l Judd) and many other land-dwelling animals. Judging from Inkling history, the Mollusc Era appears to have progressed in stages similar to that of humanity. Currently, the dominant species consist of Inklings, Octarians, jellyfish, sea anemone, and several types of crustaceans and fish, though some members of these species vary greatly in their intelligence and development.

History
The twilight years of human history had been difficult ones, marked by no fewer than five world wars and countless lesser conflicts. During the last of these world wars, a nuclear warhead hit the South Pole. The resulting atomic fireball melted the Antarctic ice cap, causing sea levels that had already risen to dangerous levels from years of global warming to reach catastrophic levels. Despite the attempts of a handful of survivors to hide away from the ensuing flood in underground cities or enter cryogenic stasis in the hope that they could reclaim their world, mankind soon went extinct.

After about 10,000 years however, the water levels began to recede, forcing many sea creatures to evolve into intelligent, humanoid land-dwellers. Upon reaching this point, these evolved species began rapidly progressing, experiencing various periods similar to humanity's own progression, but in a more compressed amount of time as a result of their discovery and reverse-engineering of human technology.

At some point during this advancement, Judd was awoken from his cryogenic stasis chamber and quickly became well-known for his ability to judge ink battles, as well as being the only intelligent creature that did not evolve from a sea-dwelling species. The first recorded Turf War occurred during a period in Inkling history with many similarities to Ancient Egypt, roughly 2,000 years before the events of Splatoon began. This event is also the first known instance of Judd being used to determine the outcome of an ink battle.

The Great Turf War
As time progressed, the Octarians separated themselves from the other species of the Mollusc Era. They became dissatisfied with the amount of available dry land and waged war on the Inklings, the other dominant species at the time, to gain total control of the turf. The Octarians constructed a variety of large machines known as the Great Octoweapons and began attacking Inkling cities. However, due to one of the Octoweapons' plugs being pulled, the Inklings secured a victory in the war and forced the Octarians to retreat to underground lairs such as Octo Valley, which were constructed from the ruins of the subterranean cities built by the remnants of humanity.

Stolen Zapfish
At one point in the events of Splatoon, the Great Zapfish and a large number of Zapfish were taken from Inkopolis into Octo Valley. Most residents of Inkopolis did not see the missing power sources as a major concern, even though Callie and Marie covered the event in Inkopolis News. However, Cap'n Cuttlefish and the New Squidbeak Splatoon, comprised of Agent 1, Agent 2, and Agent 3, traveled to Octo Valley and navigated the Octarians' network of underground lairs, eventually defeating DJ Octavio and reclaiming the stolen Zapfish. The Great Zapfish now rests on Inkopolis Tower.

Modern Age
The modern age of the Mollusc Era is dominated by a large variety of species. However, Inklings and jellyfish seem to be the most widespread organisms, seen in nearly every region of Inkopolis, and appear to be incredibly advanced. In fact, Inklings have sent records of history into space in the form of a disk in an attempt to contact extraterrestrial life(Sunken Scroll 22) The Octarians have since settled in Octo Canyon; the defeat of DJ Octavio seemed to have no major effect on their civilization, and in fact the battle between him and Agent 3 was believed to be part of an underground concert by the Octarians who witnessed it. He later tried to steal the Great Zapfish a second time, but was defeated again, this time by Agent 4. Due to not being brainwashed by DJ Octavio anymore because they heard Calamari Inkantation, many Octolings have found ways to escape the Octarian Army and have ended up reaching Inkopolis sometime during the events of Splatoon 2. Many non-sentient animals, such as sparrows, crickets, and cicadas, are also present in the modern age and appear to thrive alongside their more intelligent counterparts.

The current state of society on Earth appears to mirror a typical human urban environment, with a variety of stores, living spaces, means of transportation, and entertainment venues. Inhabitants of Inkopolis have exhibited many functions similar to those of humans, such as driving cars, riding trains, playing at a park and campground, and possessing jobs at locations such as Walleye Warehouse. In fact, many aspects of society appear to have been inspired by remnants of humanity's existence, even though archaeologists describe humans as "primitive with little intelligence" based on the size of their skulls(Sunken Scroll 26). For example, many weapons were inspired by human artifacts, such as spray bottles, gasoline nozzles, and garden hoses, and the machine used to announce Splatfest themes appears nearly identical to a classic human fax machine. It appears that at least one research facility has been dedicated to studying the relics of the lost human civilization.

Modern culture places great emphasis on the concept of being "fresh," which essentially means that clothing and skill are viewed in high regard. In fact, shopkeepers will not sell Inklings or Octolings gear or weapons until they've reached a certain level of "freshness," or skill. Music is also featured heavily in modern culture, with singing icons such as the Squid Sisters, Off the Hook, Hightide Era, and the Chirpy Chips' music being featured in nearly every part of Inkopolis.

Ink Battles
One of the most prominent features of the Mollusc Era is the presence of Ink Battles, a form of competitive sport, or, in the case of the Great Turf War, actual battle. There are many types of Ink Battles, but the most well-known form is the Turf War. Other modes, such as Splat Zones, Tower Control, Rainmaker, and Clam Blitz are typically only played by more advanced Inklings and Octolings. Inklings and Octolings are the only species known to participate in Ink Battles.

Ink Battles have influenced the culture of the Mollusc Era for over 2,000 years, bringing about mainstream weapon shops such as Ammo Knights, music, and events like Splatfest. Inklings and Octolings dress in specific styles to aid them during Ink Battles, and many begin participating in such battles at the age of 14.

Events
The Mollusc Era introduced new customs, traditions, and holidays. The most well-known event that occurs in Inkopolis is the Splatfest, which typically takes place every three to four weeks. During Splatfests, a theme is chosen live on Inkopolis News. Inklings and Octolings vote on their choice in the theme, such as cats versus dogs, and then battle in a mode similar to Turf War to earn victory for their team. Inkopolis Plaza (or Inkopolis Square in Splatoon 2) and all of the stages around Inkopolis are decorated for the event, shrouded in darkness and illuminated with glowing lights.

One of the lesser-known holidays that is celebrated during the Mollusc Era is Squidmas, which likely occurs in December and is probably based on the human Christian holiday known as Christmas. It is unknown why Squidmas is celebrated, whether for religious or cultural reasons, but it is mentioned fairly often by Agent 1 and Agent 2 in Octo Valley. Squidmas somehow involves Father Squidmas, which is actually revealed to be Cap'n Cuttlefish.

Trivia

 * The name "Mollusc Era" is only mentioned in Sunken Scrolls.