I hope it goes without saying that there are lore spoilers ahead, as well as Guild Wars campaign spoilers.
The history that's older than dirt
Way back in the dusty memory of time, there were giants in Tyria. Real, true, massive giants -- not the kind you see stomping around the Diessa Plateau nowadays. They died off or vanished about 11,000 (give or take a couple hundred) years before the present day of Guild Wars 2. A little more than eight thousand years after that, the True Gods (as recognized by the humans) brought in a race of serpent creatures to guard the world while they tinkered with it. The gods, like the serpent people, lived in the world at this time, but that doesn't mean that the gods originated in Tyria. The serpent people, known in the present day as the Forgotten (guess why before the next paragraph starts for an extra special prize!), had an advanced culture and served as the keepers of knowledge and lore within the world. They lived in peace with what creatures they could (the Charr serving as a glaring exception), and the world was pretty good for a long while. Some 1,500 years later, the humans were brought to Tyria. When I say brought, I don't mean it as in "brought up out of the dust." They, like the gods and the Forgotten, aren't from around here.
Humans, being the acquisitive lot that they are, quickly spread out and staked their territory wherever they could abide peacefully and started a war wherever they couldn't. They undid most of the Forgotten's work.
Magic and the gods
Through all of their fiddling with the world, the gods (or at least three of the six) lived in Arah (known, coincidentally, as the City of the Gods), which is part of the region known as Orr. Orr is believed to be the location of the first human settlement in Tyria, although humans also branched out to Ascalon (but remained, for a while, ruled by one king, the first of whom was named Doric). Ascalon was tricky business, as it was inhabited by the Charr, but the gods had something of a soft spot for their humans and helped them push the Charr back so that Ascalon could become a human settlement. This all happened within the humans' first hundred-ish years in Tyria. After another hundred years passed, the god Abaddon led the others in giving magic to the sentient races of Tyria, a power that all the gifted races promptly abused.
There was much fighting between the races blessed with magic, so King Doric went to Arah to plead with the gods to take their gift back. Rather than remove it entirely, the gods created a stone that contained the power of magic by preventing any one being from mastering all the schools of magic, they sealed it with King Doric's blood (only a couple of drops, don't worry! Although there is a little bit of lore hinting that he may actually have died because of it), and they broke the stone into five pieces, four of which are called bloodstones and represent different schools of magic, and one of which is called the Keystone and is necessary for uniting all the shards. These pieces were then chucked into a volcano for safekeeping. Later, the volcano erupted and spewed the pieces hither and yon. Three bloodstones, one on the Ring of Fire island chain and two in Kryta, have a known location and figure into players' adventures in Guild Wars and Eye of the North. The other two are in unknown locations.
Abaddon, the god who made free with the magic distribution originally, was upset that the other gods wanted to limit his gift, so he tried to lead a war against them. It didn't work particularly well, and he was weakened, chained, and thrown into the Realm of Torment. The Forgotten did the gods a solid by going in there with him to serve as jailkeepers from then until the events of Nightfall, a stretch of some 1,075 years.
The gods withdrew from the world and more or less ceased meddling with things.
The Forgotten who weren't watching an insane god in a place that looks like somebody turned giant living beings inside out waited another hundred years or so and then withdrew to the most remote corner of Tyria, where humans couldn't go. They waited in the Crystal Desert and became the caretakers of a dragon named Glint.
Only about 1,200 years to go
Glint compiled the Flameseeker Prophecies 272 years after the Exodus of the Gods. These prophecies were brought to bear in the events of the aptly named Prophecies campaign.
Kryta was established as a colony of Elona and then became an independent nation 358 years after the Exodus (hereafter, such dates will be referred to as [year] AE, in keeping with in-universe reckoning).
"The Mists touch all things. They are what binds the universe together, past, present, and future. They are the source of all good and evil, of all matter and knowledge."
In 851 AE, an arcanist by the name of Lord Odran became the first human to enter what is known as the Rift (which is what the Forgotten came to Tyria through, according to some lore), which is a timeless location at the center of the Mists. The Mists are effectively the source of life as we know it -- the proto-matter from which reality was built. They exist between worlds and are, both in lore and as a gaming abstraction, the location of a lot of the PvP and two of the elite areas in Guild Wars.
Within the next 50 years, the Charr discovered the Titans and the Flame Legion, one of the four High Legions of the Charr (the other three of which are the playable factions for Charr in Guild Wars 2). The Charr declared the Titans to be deities, and the humans erected the Great Northern Wall. You might consider that there could be a relation between those, as the Wall was built to keep the Charr (who were starting to be a threat once again) out of Ascalon. (Also, it later turns out that the Titans were totally working for Abaddon all along and drove the Charr to invade the human nations on his orders.)
In 1013 AE, the titular Guild Wars began. The Guild Wars were fought between the established human kingdoms of Ascalon, Kryta, and Orr. The fighting was brought to an end in 1070 AE, the very start of Guild Wars, by the Charr invasion of Ascalon. This invasion is known as the Searing.
The Searing threw the human nations' defenses into something of a shambles, and the Charr were able to push through to Orr and threatened to march on Arah itself. Rather than letting the Charr overtake the City of the Gods, a human vizier by the name of Khilbron found scrolls of forbidden knowledge in the catacombs beneath Orr and unleashed a tremendous magical force. This resulted in the Cataclysm, which more or less destroyed Orr and sunk the city of Arah. The Vizier, players later find out, was corrupted by Abaddon in the twisted god's attempt to destroy the holy city. He becomes a Lich and the big bad at the end of Prophecies (although, interestingly, much of his backstory isn't discovered by players until Nightfall).
Fast-forward to Kryta, where there are heaps and scads and swarms of undead. Kryta is being run by the White Mantle, an order that players find out over time reveres the mysterious Unseen Ones. Players help the head of the White Mantle, Confessor Dorian, secure an artifact of untold power: the Scepter of Orr. After that, the White Mantle leaders swear that you and they are best buddies, and as a special honor, players can help them out by tracking down the Chosen, special Krytans who are deemed to be worthy of getting a cushy life of study and devotion.
The Chosen whom players help find get kidnapped by the Shining Blade, a covert group that's working against the White Mantle. Players then find out that Chosen are actually being slaughtered (atop one of the ancient bloodstones, no less!). In an attempt to fight back against the injustices of the White Mantle, players and the Shining Blade ally themselves with some dude named Vizier Khilbron, give him the mighty Scepter of Orr because, I guess, he asked nicely, then flee to the Crystal Desert. There they meet the Forgotten, find Glint, and learn of the Flameseeker Prophecies. The Unseen Ones turn out to be Mursaat, an ancient and hostile race of flying magic-users. Vizier Khilbron promises that everything will totally be completely OK if the players just go to the Ring of Fire islands and nope he's a Lich and he was lying and you just let Titans loose in the world! Ticked that the Lich managed to make patsies of them for so long, players strike back, destroy Khilbron, set things to rights, and then move on to hard mode, farming, and waiting for the new campaigns.
Elisabeth Cardy is a longtime Guild Wars player, a personal friend of Rytlock Brimstone, and the writer of Flameseeker Chronicles here at Massively. The column updates on Tuesdays and keeps a close eye on Guild Wars, Guild Wars 2, and anything bridging the two. Email Elisabeth at firstname.lastname@example.org.