Up until the late Merethic Era, the elves had lived in peace with the Atmoran settlers of Skyrim. When they saw that humankind was growing at an exponential rate, given a human's faster reproductive period, the elves started a genocidal campaign against them.
Almost the entire human population of Skyrim was wiped out. Only three people were purported to have survived the attack on the capital city of Saarthal. They were Ysgramor and his two sons, Yngol and Ylgar.
They escaped Skyrim on the last longboat back to their homeland, Atmora. The night the elven genocide began became known as the Night of Tears. Upon arriving to Atmora, Ysgramor told stories of treacherous elves and of gathering an army to come back and avenge the lost souls.
Return of the menEdit
On the day known as Day of Final Passage Ysgramor and his army, the Five Hundred Companions, left the port of Jylkurfyk on the continent of Atmora, to sail back to Mereth and take back what was rightfully theirs.
During their voyage to Mereth, The Five Hundred got caught in the Storm of Separation. As a result, the legendary Ysgramor lost his eldest son, Yngol. Yngol Barrow was made as a proper burial place for an Atmoran warrior.
Shortly after the Five Hundred arrived at Hsaarik Head, Saarthal was taken back from elven kind. The first goal of the Five Hundred was fulfilled and the next was yet to plan. The Circle of Captains was assembled and it was decided that every captain and his crew should go their own ways. Thus began a period of genocidal slaughter of elves.
The first notable event to be recorded was the founding of Whiterun. The crew of the Jorrvaskr under command of Jeek of the River scouted the area later named Whiterun Hold. They found a mysterious monument that was feared by local elves and decided to put it to proper use. The lands in this valley were suitable for harvest as well. The crew settled there not knowing that they had started a settlement that would later grow into a great city that still stood in Fourth Era.
The second notable event to be recorded was the founding of Windhelm. The crews of the Kaal Kaaz, Sadon Reyth and Ylgermet, under command of Harbinger Ysgramor himself, fought elves in the area later named Eastmarch. Ysgramor stumbled upon his son's grave and in his grief decided to build a great city where the nearby river, White River, met the Sea of Ghosts. The city was to serve as a monument of all mankind. It was built by elven captives in Atmorian fashion. A long bridge was built as the only entrance to the city, so that no elf could sneak in unnoticed to avenge his own kin. As well as Whiterun, Windhelm still stood in the Fourth Era as one of the biggest cities in Skyrim.
End of the ReturnEdit
The period along with the great expansion of mankind and a merciless reprisal campaign against the elves ended with the death of Ysgramor. News of his death spread like a dark cloud all over Tamriel, and most of the warriors put down their weapons in grief never to pick them up again. Ysgramor chose to be buried at sea, looking in the direction of his true homeland, Atmora. But even after death of the great Harbinger, his castle served High Kings for many generations after.
However, by the end of the Return, Man had already gained a permanent standing in Skyrim. Snow Elves had been banished underground, to emerge only thousands of years later as the beasts known as Falmer. Tamriel soon became the only home for men, as Atmora had froze beyond recognition and had ceased to be a haven of settlement and survivability.