I wrote a Legends timeline for a friend last year. I apologize for any spelling errors and bad formatting or if anything isn't 100% correct - I was mostly going off memory and I haven't kept up with the TOR MMO.
PART I
BETWEEN 27K BBY AND 20K BBY - THE FIRST GREAT SCHISM AND THE GALACTIC REPUBLIC
-The Rakata Infinite Empire collapses when the Rakata are struck with a mysterious plague that deprives them of the ability to use the Force.
-The human despot Xim wars with the Hutts for control of a large portion of the galaxy but is killed.
-The Jedi are thrown into chaos in the First Great Schism when Xendor, who believes the Order has become too stagnant and dogmatic, begins researching into the dark side. He and his followers are expelled and exiled to the planet Lettow, where they form the Legion of Lettow. The Legion wars with the Jedi but are annihilated.
-After reverse engineering Rakatan hyperspace technology, humans from the core worlds - led by Corellia and the human homeworld of Coruscant (formerly Notron) form the Galactic Republic. They come in contact with the Jedi Order, who agree to serve the Republic.
-The Honorable Union of Tion and Desevro becomes aware of the Galactic Republic and attempts to conquer it to prevent a rival power from growing. The Republic successfully pushes back and destroys its opponent, but the brutal manner in which it does so causes the Jedi to break from them. The Jedi eventually return to their alliance with the Republic not to act as soldiers but as watchdogs.
-At some point, a creature of the Force known as The Entity nearly conquers the galaxy but is defeated by the Jedi.
20K BBY - THE EXPANSION ERA
-The Republic begins an era of expansion, bringing it into contact with other civilizations.
17.5K BBY
-The Republic stumbles upon the Duinuogwuin, commonly known as "star dragons", who chase their scouts back to Coruscant and attack the planet. When the Chancellor learns that the Duinuogwuin are sentient, he establishes contact and forms peaceful relations. Philosophers of the Republic and the Duinuogwuin establish the University of Coruscant.
17K BBY
-The first of seventeen Alsakan conflicts - territorial disputes with the rival league headed by the planet Alsakan - occurs.
15K BBY
-In another galaxy, the living planet Yuuzhan'tar is invaded by two species of sentient droids - the Abominor and the Silentium. The war ravages the planet and its inhabitants, the Yuuzhan Vong, come to view non-organic technology as a heretical abomination to their religion. A civil war erupts after the successful repulson of the droids, known as the Cremlevian War, which destroys Yuuzhan'tar; as its last act, the planet severs the Yuuzhan Vong's ties to the Force. A seed of Yuuzhan'tar that becomes the planet Zonama Sekot separates from its mother and drifts through space. The Yuuzhan Vong wander through the void of intergalactic space to find a new home.
12K BBY - THE PIUS DEA ERA
-After centuries of plotting, the radical religious movement known as Pius Dea ousts the chancellor of the Republic in a coup and installs their own leader, Contispex, as chancellor. The Jedi sever their ties with the Republic, which begins to carry out massive and zealous crusades against "heretical" worlds opposed to the order.
11K BBY
-The Jedi, Republican loyalists, and Renunciates (members of Pius Dea who have lost their faith) manage to overthrow Contispex XIX and return the Republic to secular rule.
7K BBY - THE SECOND GREAT SCHISM AND FORMATION OF THE SITH
-The Second Great Schism occurs when a group of Jedi desire to use the Force to create life. They succeed in creating new species of animals but the power is seen as so dangerous that the Jedi Order refuses to allow it. War breaks out between the Jedi and the rebels, who increasingly use the dark side in their quest to harness the full power of the Force, but the rogue Jedi are defeated and exiled to space.
6900 BBY
-The exiled Jedi, under the leadership of Ajunta Pall, land on Korriban, homeworld of the much more primitive Sith species. The Sith are impressed by their technology and welcome them but Pall's followers overthrow the king and subjugate the Sith race. They take up the title "Dark Lords of the Sith" and over time become associated with the name of the species itself, which mostly dies out through oppression and interbreeding. The Sith Order becomes the most notable enemy of the Jedi.
-The Sith lady Sorzus Syn creates a number of mystical amulets through Sith alchemy; using one of them, she captures the soul of the Sith lord Karness Muur. She also formulates the original version of the Sith Code.
5100 BBY - THE GREAT HYPERSPACE WAR AND FORMATION OF THE SITH EMPIRE
-The half-breed Sith Lord Marka Ragnos comes to power. He is regarded as the strongest Sith of his time.
5000 BBY
-Marka Ragnos dies and the Sith Lords Naga Sadow and Ludo Kressh duel while being watched by his spirit to determine who will become the new Dark Lord of the Sith. Naga Sadow is victorious and when Republic scouts accidentally discover Korriban, he gives the order to follow them back and invade Coruscant, beginning the Great Hyperspace War. The war is incredibly destructive but the Republic's superior technology and the disunity between Sadow and Kressh's forces allow the Republic to quickly defeat the Sith.
4999 BBY
-The pureblood Sith Lord Vitiate, born Tenebrae, who had been made lord of the planet Nathema by Ragnos, calls together eight thousand Sith Lords and - having perfected an extremely powerful and secret rite - murders all of them, as well as millions of other sentient beings and indeed every living thing on the planet - and absorbs their life forces, allowing him to gain immortality. Vitiate adopts the title of Sith Emperor rounds up what is left of the scattered Sith Empire. With Korriban destroyed, they set out to find a new homeworld.
-One of the ships from the exodus is lost and crashes on the world of Kesh. Over time, the people form the Lost Tribe of the Sith; although they believe themselves to be descendants of great conquerors, they are actually descendants of servants of the Sith Emperor.
4980 BBY
-The Sith Emperor's fleet arrives on Dromund Kaas and begins rebuilding the Sith Empire.
4400 BBY - FREEDON NADD AND THE SITH
-The Jedi padawan Freedon Nadd is passed over for knighthood and in a rage murders his master. He flees to space and finds the spirit of Naga Sadow on Yavin IV, where he becomes his apprentice. Nadd learns the ways of the dark side and upon deciding that he is powerful enough he destroys Sadow's spirit. Nadd conquers the planet Onderon and makes himself king, establishing a line of dark side monarchs. He banishes criminals to the outskirts of the capital city, Iziz, who learn how to tame wild beasts. The Beast Riders begin raiding Iziz and the so-called "Beast Wars" begin.
4300 BBY
-Freedon Nadd dies
4250 BBY - THE THIRD GREAT SCHISM
-The Third Great Schism occurs in the Jedi Order when rogue Jedi who wish to use the dark side are defeated in battle and exiled to space. They find the Vultar system and an ancient Celestial artifact - the Cosmic Turbine - but upon activating it destroy themselves and the entire solar system.
4175 BBY - THE GREAT DROID REVOLUTION
-The Great Droid Revolution occurs on Coruscant but is put down.
AROUND 4100 BBY
-The Sith Emperor begins formulating a plan to expand the ritual that granted him extended life by encompassing all life in the galaxy, with the intention of becoming a god. He waits for galactic events to align in a way that will allow him to cause a war that will allow him to absorb enough life energy from the resultant mass death. The Dark Council becomes aware of his plans and secretly tries to undermine him but he frustrates their schemes.
4000 BBY - THE FREEDON NADD UPRISING
-After Onderon comes in contact with the Republic, the Jedi send Arca Jeth and his padawans (including Ulic Qel-Droma) to help the royal family put down the Beast Riders. However, when Princess Galia lets herself by kidnapped by a Beast Rider with the intent on marrying him, Jeth learns that the royal family under Queen Amanoa are dark side users and decides instead to help the Beast Riders overthrow the government. They succeed and Galia assumes the throne.
3999 - 3950 BBY - THE OLD SITH WARS (THE GREAT SITH WAR, JEDI CIVIL WAR, SITH CIVIL WAR, AND FIRST JEDI PURGE)
-The Keto cousins from the Empress Teta system, who had been on Onderon to learn dark arts from the royal family, find the spirit of Freedon Nadd and become his disciples. They return to their homeworld and take over, founding the Krath movement.
-The Freedon Nadd uprising led by king-in-exile Ommin and other loyalists begins. Ulic Qel-Droma tries to assist the royal house but is injured by Ameena Keto who poisons him with dark arts and begins to turn him to the dark side.
-Arca Jeth is killed by Krath war droids.
-A slivilith - a semi-sentient creature sent as an advance scout by the Yuuzhan Vong - enters the galaxy but flees after it is attacked.
-Ulic Qel-Droma kills Ameena Keto's partner and joins her as the head of the Krath movement. The Jedi under Nomi Sunrider stage a rescue attempt but he refuses to go with them. The power hungry Jedi Exar Kun abandons the order goes to Yavin IV to study Sith secrets. He encounters the Massassi people and traps the spirits of the ir children in a glowing golden orb to extract their powers. Kun finds Freedon Nadd's spirit in his tomb; he learns from him and then destroys him, as Nadd did to Sadow. Kun and Qel-Droma battle as rivals but the spirit of Marka Ragnos recognizes them as Sith and makes Kun the master and Qel-Droma the apprentice. They work together to create the Sith Brotherhood.
-The Jedi deploy an orbital bombardment on Yavin IV to try and kill Kun but he escapes. They build the so-called Lost City of the Jedi to help rebuild the ecosystem.
-Qel-Droma and Exar Kun lead the Krath in the Krath Holy Crusade and engage the Republic in the Great Sith War. Qel-Droma also secures the help of the Mandalorians after dueling and defeating their leader, Mandalore the Indomitable. The Great Sith War wreaks havoc across the galaxy and causes great destruction. Qel-Droma kills his own brother in battle and the Jedi Order, in an effort to stop his growing power, uses advanced Force techniques to sever Qel-Droma's connection to the Force itself. Left powerless, Qel-Droma comes to his senses and repents. He turns the war on its head and leads Republic and Jedi forces against Kun, killing him in battle. Qel-Droma goes on to retire from public life and take on a padawan but is assassinated by a space pilot named Hoggon obsessed with finding fame.
-The First Watch Circle, a small group of advanced Jedi seers, learn of the Rogue Moon prophecy that states that a figure of darkness will soon come to power and bring woe to the galaxy. Fearing that one of their padawans may be the figure, they murder them in the Padawan Massacre, but the padawan Zayne Carrick escapes.
-The Mandalorians, now under Mandalore the Ultimate, and egged on by the Sith Empire continue their skirmishes with the Republic over the next thirty years in the Mandalorian Wars, mostly raiding and conquering planets in the outskirts. After they carry out genocide against the Cathar people and begin to push inwards towards the core, a number of Jedi desire to take action. The Jedi Council prefers to stay uninvolved but some Jedi under a rogue Jedi known only as "the Revanchist" break ranks and help put down the Mandalorians. In the Battle of Malachor V, he ends the war by destroying the Mandalorian fleet - and a good portion of the Republic's - by igniting the Mass Shadow Generator, a superweapon that wipes out the entire enemy opposition and cracks the planet Malachor V. The Revanchist takes on the shortened name Revan.
-Zayne Carrick's Rogue Moon Organization uses the money that he obtains in cons and swindles while living on the run to aid survivors and refugees of the Mandalorian Wars.
-Zayne's ally, a Jedi named Celeste Morne, is possessed by the spirit of Karness Muur when she comes in contact with the Muur Talisman. Zayne seals her away in Dreypa's Oubliette, a stasis pod created by the ancient Sith lord Remulus Dreypa to preserve life indefinitely.
-Revan and his friend, a Jedi named Malak, go into the heart of the Sith Empire to confront the Emperor himself. The Emperor defeats them and corrupts them, turning them to the dark side of the Force as Darth Revan and Darth Malak.. He sends them out to find the ancient Rakatan Star Forge to use as a weapon against the Republic, but they manage to break free of his control. However, Revan and Malak determine that the Jedi are no match for the Sith Empire and desire to use the dark side to protect the Republic from the greater threat; therefore, they form their own rival Sith Empire and launch a war to conquer the Republic.
-The so-called Jedi Civil War rages for two years as Revan and Malak sway Jedi to their cause. It finally ends when the Jedi Bastila Shan captures Revan and, with the help of other Jedi, wipes his mind. Revan is "reprogrammed" to become a loyal Jedi again and leads the counterattack against Darth Malak's Sith Empire. Revan battles Darth Malak on the Star Forge and kills him.
-In the wake of Malak's death, the Sith of his empire fracture and begin fighting over territory in the Sith Civil War. Ultimately three dark lords emerge in the Sith Triumvirate - Darth Nihilus, Darth Sion, and Darth Traya - who rule the tenuous empire.
-Revan retraces his steps to try and recover his memory and finds his way back to the Sith Empire. He conspires with Darth Nyssa, who wants to prevent the Emperor from going through with his plan to cause a galactic war to absorb the energies of the dead; they manage to get the Emperor's advisor Scourge on their side but when they attack the Emperor, Scourge has a vision that they will fail and another will strike down the Emperor in the future. He turns on Revan and Nyssa and helps the Sith Emperor defeat them. Nyssa is killed while the Emperor grants Scourge an extended lifespan and promotes him to the position of Emperor's Wrath. He also curses Revan with an extended lifespan and imprisons him in an impregnable Maelstrom fortress in solitary confinement.
-The Triumvirate uses Sith assassins to wipe out what Jedi remain after the devastation of the Jedi Civil War in the First Jedi Purge. When the few hundred remaining Jedi have a conclave on Katarr, the Sith bomb them and wipe out almost all remaining Jedi. Using the same technique that the Sith Emperor used to expand his lifespan, Darth Nihilus absorbs the energies of the dead Jedi.
-Meetra Surik, known as the Jedi Exile after she was kicked out of the order for aiding Revan in the Mandalorian Wars, survives the purge and kills all three members of the Sith Triumvirate in battle. She goes on to rebuild the Jedi Order while the remnants of Malak's Sith empire completely collapse and dissolve. A few Sith from Malak's line of protégées remain for some centuries in secret but eventually die out.
-The Sith Emperor desires to invade the Republic with the Jedi nearly wiped out but due to having a psychic link to Revan which allows him to extend his lifespan to torture him, Revan is able to turn the tables and influence the emperor to slow his plans. He is not able to completely stop the buildup to war, but over the next three hundred years the Republic is at peace, unaware of the growing threat.
-Without the planned war to prolong his lifespan, the Sith Emperor dies his first natural death but successfully transfers his essence into another body. The Emperor prepares a number of bodies, known as "Voices of the Emperor", so that he can transfer his essence any time he dies.