Dark Ages (also known as Antiquity (古代文明 "Kodai Bunmei") outside of the SNES/PSX versions) is the year 12,000 B.C. in Chrono Trigger. This is the era of the fall of the Kingdom of Zeal, which abused the power of Lavos and sank to the bottom of the sea. Those born after this time period are unable to naturally use magic.
Geography and climate
The entire surface of the planet is covered by a never-ending blizzard. The much warmer Kingdom of Zeal floats above the frigid clouds of the lower atmosphere and dominates most of the planet. After the Ocean Palace incident, Lavos destroyed the Kingdom of Zeal and it fell from the sky. This caused a massive tidal wave that flooded most of the planet, as well as cleared the clouds in the sky and allowed the planet's surface to be warm again.
The climate in the Kingdom of Zeal is apparently temperate due to the existence of green plants and liquid water; this indicates that a strong and permanent temperature inversion dominated the atmosphere of this era, and the collapse of Zeal likely resulted in the destruction of this inversion.
There is only one gate that the player finds after Lavos falls from the sky in Prehistory, which leads to a cave on the surface in 12,000 BC.
Magus is the only playable character from this era.
A great deal of the history of the Chrono Trigger world is explained in this time period and its connection to magic and Lavos.
After defeating the Reptites, Crono and his party witness Lavos arriving at the planet. It quickly buries itself underneath the surface and leaves behind a time gate which Crono and his party travel through. It brings them to the year 12,000 BC, a time when humans are divided between magic wielding Enlightened Ones and the castaway Earthbound Ones. The Earthbound Ones live on the surface of the planet, which is covered by a never-ending winter which was caused when Lavos struck the planet. Crono and company find the Kingdom of Zeal, home to the Enlightened Ones, a floating paradise above the clouds. When they arrive at the Queen's Palace, they are identified as a threat by the "Prophet", who is Magus in disguise. Magus was sent back here during his encounter with Crono's team in his lair and became a Prophet to the people of Zeal due to his knowledge of future events. Crono and his party are defeated by Queen Zeal and Dalton and held the prisoner in the palace. Schala frees them, but before they can get far the Prophet forces Crono and his friends back through the time gate, and has Schala seal it behind them, but not before they learn that Melchior is being held prisoner at a place called The Mountain of Woe, and that the denizens of Zeal draw their magic directly from Lavos using the Mammon Machine.
2nd VisitAfter acquiring the Epoch, Crono and his friends rescue Melchior from Mt. Woe and meet with Schala and the Earthbound Ones in a cave on the surface. Melchior devises a way to destroy the Mammon Machine using a Ruby Knife. The cave is attacked by Dalton's force and Schala is taken to the Ocean Palace. Crono and his party battle their way through the Ocean Palace until they reach the Mammon Machine's chamber. Queen Zeal is using Schala to draw untold amounts of energy from Lavos, which causes the beast to awaken. Magus reveals himself, and attempts to kill Lavos but is easily defeated. Crono is killed by Lavos when he steps in front of the beam to save his friends. Lavos then proceeds to destroy the Ocean Palace and fires beams of energy into the sky, destroying the Kingdom of Zeal and sending it crashing down to the surface. The impact causes a massive tidal wave that floods most of the planet's surface. Schala teleports Magus and the remainder of Crono's team to safety, her own fate remains unknown until Chrono Cross.
While the survivors regroup on the surface and form Last Village, Dalton flies in with the Blackbird and declares himself the new "King" of Zeal. He steals the Epoch and takes Crono's friends prisoner. They escape, destroy the Blackbird, and send Dalton through a time gate. At this point, the player confronts Magus back on the surface and can choose to either kill him or take him in as a party member. Either way, he will reveal a way to bring Crono back to life.
Eventually, the remainder of the Ocean Palace rises into the sky as the Black Omen. Queen Zeal is still alive inside, bound to Lavos, and possibly immortal. The Enlightened Ones who survived the destruction of Zeal no longer have magical powers and now live amongst the Earthbound Ones. The surface dwellers would go on to form the various kingdoms of the Middle Ages.
In Chrono Cross, the Time Crash sends Chronopolis from the year 2400 AD then to the year 12000 BC. To counterbalance the new presence, the Entity drags in from another timeline Dinopolis, leading the researchers to send war machines to attack the Dragonians. Once the war was over, FATE decided to construct its own paradise; though its primary objective was to not disturb history until the future came by not making contact with the Zenan mainland, FATE drew up a plan that would allow it to create its own civilization and preclude any outside contact. It terraformed the archipelago of El Nido and selected several staff members to populate the islands.