It spans the universe.
No city in Azeroth can do what the Exodar can. Repaired at last, the Exodar is no mere fortress but rather a satellite of the great Tempest Keep brought to Outland by the naaru. As a result, the Exodar possesses the power to bridge the gulf between worlds, traveling through the Twisting Nether. And after years spent crashed into Azuremyst Isle, the Exodar is fully operational.
But in her turn, the Exodar is more than a vessel. The means of escape for Velen and the draenei who survived the assault of the blood-maddened orc butchery that reduced them to hiding in Zangarmarsh, the Exodar carried them forth after it had been liberated from the blood elves who had invaded Tempest Keep proper. Sabotaged by those same blood elves, servants of Kael'thas Sunstrider, the Exodar's crash landing was yet another travail for the draenei to overcome. But on Azeroth, they found a refuge from the Burning Legion and the will to move forward as members of the Alliance.
It was to the Exodar that Prince Anduin Wrynn of Stormwind came to study the way of the Light under Velen, and in so doing, in time introduce the draenei way of viewing the Light to the Eastern Kingdoms. It was at the Exodar that Velen pledged that the draenei would not leave Azeroth to fend for itself but would stay and defend their new home.
The Exodar spans the universe, right from where it sits today.
The Exodar as it stands today in game is actually somewhat behind the times. As mentioned in the Velen leader short story, since the ship crash landed, the draenei have been working to repair the vessel and restore its dimensional travel capabilities -- and they have succeeded. At present, with the ultimate fate of Tempest Keep unknown, the Exodar is the only dimensional ship known to be in the hands of a mortal (albeit ridiculously long-lived) race.
What this means is that, unlike when they were stranded on Draenor when K'ure's ship crashed and became Oshu'gun, the draenei on Azeroth are not trapped. If the orcs or any other mortal race became corrupted by the Legion and sought to destroy them, this time, they have a way out.
For that matter, the draenei who have survived to populate the city that is also a vessel are the last, most hardened survivors of their people. The breathing room bought by the arrival on Azeroth has not been long enough to erase decades of near-total genocidal attacks upon them by the orcs, nor has it caused them to forget the blood elf assault on Tempest Keep that forced them to steal the Exodar back in the first place. While the blood elves' sabotage of the Exodar's engines ended up turning out for the best for the draenei, they're not a people who have forgotten just how close they came to being totally destroyed, as seen in the end of the Velen short story. The Vindicators can and will kill to protect their people and their leader.
In a way, the Exodar has changed the draenei as a people. It is a symbol of their escape from near destruction; their return to Outland during the events of The Burning Crusade was made possible by their having escaped in the Exodar and found allies among the mortal races of their new home. Furthermore, characters who leveled up through The Burning Crusade's content saw the process of the draenei's progression through their new allies' lands and their coming to know Azeroth.
Without the Exodar, paradoxically, the draenei could never have reclaimed as much of Outland as they have. They could never have re-established contact with those broken that they did in Nagrand and Orebor and Shattrath, and they would not now be capable of escape -- or, perhaps, of spearheading future efforts.
It was in first contemplating the events of Prophet's Lesson that I started to realize that the Exodar not only serves to prevent the events of their past from ever taking place, but it also serves to potentially change the future. For the first time, mortals have the power to travel the cosmos without dangerous and unstable portals.
The crystalline magics of the naaru are clearly under the draenei's control. It wasn't O'ros who ordered the vessel ready for departure; it wasn't even Velen. It was the draenei themselves, left without Velen's guidance and council, who made the decision. And the ship, their brother, allowed it.
Beyond a city, beyond a device, beyond a vessel the Exodar is. And everything that is, is alive. So too the Exodar. And in living, and being, it provides more than a refuge for the exiles and provides more than a means of travel. The magical secrets of the Exodar are in draenei hands -- draenei who have been ordered by Velen to go forth into the world and heal its hurts, to make ready the way for the ultimate war against the darkness. Sealed in his chambers, Velen has a vision of this war while speaking to Prince Anduin.The Exodar wasn't merely a machine to the draenei, but a living thing, a brother in a sense that the other races would never understand. And its pain had been righted, its essence healed. The Prophet rejoiced with his entire race at the triumph.
Instead of the prince, an armored warrior stood before him, his plate helm and breastplate shining with the essence of the Light itself. The warrior wielded a sword forged from the same material as the armor, held it aloft as he perched on an outcropping... Whether it was on another world or Azeroth, Velen couldn't quite tell. And suddenly the dark sky above erupted with the combined chivalry of Azeroth's races. The blood elves, orcs, trolls, tauren, and even the accursed undead and scheming goblins rode flying mounts of every sort and description. They were armored and armed in magical weaponry glowing with so much power it hurt Velen's eyes to look at them. Beside the legions of the Horde, the ancient night elves charged with humans, dwarves, and gnomes, whose ancestors formed the original Alliance, and the shape-changing worgen were united with them. Velen's own draenei bolstered the army, their ranks adorned in otherworldly metals and bearing crystalline maces and swords.This is important not only for the message of cooperation and its necessity that it imparts, but consider this: Where does this future contingent of Azerothian heroes get these astonishing weapons, glowing with the Light and magical power, these otherworldly metals and crystalline maces and swords? Where do they learn to forge this panoply? From the Exodar.
More than a city, more than a vessel, their brother showed them how to repair it, and in so doing taught the magically gifted draenei, the last survivors of the true eredar who were so potent magically that Sargeras himself visited them, the secrets of the naaru themselves.
But the importance of the Exodar's arrival transcends that. The anabasis of the draenei has placed them on Azeroth at this exact moment when the world, broken, needed repair, and in doing so, it has given the draenei the perfect opportunity to do what Velen has said must be done. As the draenei go out into the world to help rebuild and repair it, to inspire and guide, they do so with the knowledge gained from their work to heal their brother the Exodar. They will of course share this knowledge, as they have been instructed to do, to aid and inspire their allies and eventually the entire world.
The future is never set. But will the brother to the draenei let its brothers and sisters work alone, unaided? They saved and awoke the Exodar, and it clearly seeks to aid and support them in turn. The future is built on such resolve.
While you don't need to have played the previous Warcraft games to enjoy World of Warcraft, a little history goes a long way toward making the game a lot more fun. Dig into even more of the lore and history behind the World of Warcraft in WoW Insider's Guide to Warcraft Lore.