About 21,000 years ago, the naaru observed the fall of Sargeras, his depression and subsequent corruption, and followed him to the planet Argus, observing from a careful distance to see what exactly the former Titan follower of order and peace was up to. When they discovered the depths of his corruption, they were horrified -- but they had a spark of hope in the form of Velen, who despite being promised all kinds of power, refused to become one of Sargeras' army. He was not alone in these beliefs; there were other eredar that felt the same way. When he prayed, desperate for help against the corruption that threatened to overcome the entirety of the eredar race, the naaru answered. In Velen was hope, hope for peace, prosperity, happiness and the Light that the naaru sought to spread across the universe.
Velen was a seed, the start of something much larger. For the naaru knew that in order to fully defeat the Burning Legion, they would have to spread this awareness of the Light that they'd been carefully cultivating until it shone brightly enough to defeat any darkness that dared to threaten it. They spoke of this to Velen and the draenei, telling them that there were other forces in the cosmos that would stand against the Burning Legion as well. The Titans that roamed the universe, placing order and creation where there was none, were a good start, but the naaru would have to recruit many, many more followers into their fold in order to create the kind of pure connection required between universe and self that would defeat the Burning Legion.
To that end, the naaru split -- some stayed with the draenei, the first "children" of the naaru, to watch over and protect them. Others traveled to other worlds in the universe, to try and cultivate the Light within other races. Two of these naaru, E'lune (or Mu'sha), and An'she, traveled to a small world the Titans had visited and organized called Azeroth. Upon arriving, the two had a small squabble. While E'lune felt that the direct approach was the best way to spread the Light, An'she didn't want to alter the natural creatures of the little planet. E'lune wanted to do what had been done with the draenei: direct intervention. An'she thought that the creatures of the world should be observed and slowly nudged in the proper direction rather than pushed by force, as E'lune suggested.
In the end, the two parted ways, agreeing to simply work each in their own way to the best of their abilities. After all, what mattered was the message of the Light, the peace it would bring and the defeat of the Burning Legion. E'lune soon found herself attracted to a strange pool of water that pulsed with the magic of the arcane and nature, the apparent source of the world's magic and power. This would be an excellent place to focus her efforts and cultivate a race that would be just as powerful as the draenei. And so E'lune sent out a call, a soft song of peace and the Light, and waited.
An undetermined amount of time passed, until one day a group of creatures native to the planet -- strange, violent little beings called trolls -- came to the waters of the well in response to the call of E'lune. These trolls were awestruck at what they found: pure, unadulterated Light in all its glory, a Light that spoke to them of peace, of the connection between the universe and the trolls themselves. It spoke of the need for an army, a strong army that could defeat an enemy far greater, far more powerful than anything the trolls could possibly imagine. In the face of a creature of such raw power, a god in the eyes of the primitive trolls, they agreed and swore themselves to E'lune.
In gratitude, E'lune granted them an "improved" form -- lengthened their bodies, straightened their backs and gave them the power of the Light to heal and protect their brethren. The eyes of the trolls -- now night elves -- shone with the brilliant reflection of the blessed Light of E'lune. The night elves prospered, and E'lune continued to watch over both them and the strange Well of Eternity that fueled the natural magic of the world.
In time, E'lune observed Malorne, a powerful creature native to Azeroth that watched over and cultivated the natural magic of the world in ways beyond her comprehension. To this demigod she also spoke, but Malorne was unwilling to change himself, as he was intertwined with the world in ways E'lune could not understand. Instead, he created Cenarius, an offspring who was just as connected with the earth and nature as he himself was, in an effort to help the cause of E'lune in what little way he could. E'lune granted Cenarius the same powers that the night elves now possessed, and Cenarius evolved into a being that was part nature, part Light, and used the two powers seamlessly in what we recognize as the druidic powers of present day.
E'lune asked her son to teach her other children, the night elves, those druidic arts that she herself could not simply grant, and Cenarius agreed. But the night elves were unfortunately not just E'lune's children; they were also creatures of Azeroth and as subject to corruption as anyone else. Fascinated by the powers of the Well of Eternity, a section of night elves chose to devote their time to understanding and using the powers of the Well rather than following the teachings of E'lune. This captured the attention of the Burning Legion and led to the Sundering of Azeroth.
E'lune was horrified but continued to teach those of her children who would still listen and work her powers of persuasion on the other creatures of Azeroth.
Meanwhile, An'she had settled on the other side of the world to observe. He observed E'lune's activities, he observed the Sundering, he observed the natural races of the world and the best ways to reach out to them. He watched the earthen, felt their pain at the rending of the world and their deep connection to it, and watched as they hid themselves away and hibernated, all the while growing softer, weaker. And he watched the vrykul of the north and their strange, smaller children that were abruptly tossed out and forced to fend on their own. Shunned by their people, in much the same way as the draenei ... And one day, An'she finished observing and began to act.
He spoke softly to these creatures of the world, the humans who been cast out by their stronger, more violent ancestors. He spoke to them of peace, of the Light, of the inherent connection between the universe and all things in it. He spoke to them of the power of the Light, and how the Light should be cultivated, how it was naturally meant to be shared with others. And eventually, these small creatures began to listen and slowly started to practice the teachings of the Light with no intervention by An'she himself. Pleased, An'she taught them how to harness the powers of the Light so that they could practice it in earnest. Those who listened, truly listened, and followed the proper path were rewarded with the healing powers of priests and paladins.
But some creatures had been forgotten -- the tauren, a race that had been there since the dawn of time. The tauren knew that E'lune and An'she existed. The world they were so deeply connected to was changing as a result. They knew of E'lune, or Mu'sha, through Cenarius, who sought out the tauren and taught them a little about natural magic before turning his full attention to the night elves created by his mother. The tauren learned of the ways of Cenarius, who had been granted half his powers by E'lune. But the little race of nomads had yet to realize their full potential, though they knew something was ... lacking.
All right, enough with story time. With the introduction of Cataclysm, the tauren will learn how to harness the powers of An'she, and it's been repeatedly posted by Kisirani that the tauren paladins will call themselves Sunwalkers. This makes sense if you consider they will be following the Light of the "sun," or An'she. While speculation exists that the tauren will be following a different path of the Light, I like to think that all paladins, all priests, draw their Light magic from the same source -- the glimmering light of the naaru that seek to overthrow the Burning Legion and bring peace to the universe once and for all.
Unfortunately, we've been given very little information so far to confirm this one way or another, but there are many different ways that tauren paladins and priests could naturally fit in, given existing lore and the holes within that lore that have yet to be explained. This is my theory: it's all the naaru. Every last bit of it. What's your "Tin Foil Hat" theory? Got a different explanation that could make perfect sense? Leave a note in the comments, as discussion is always encouraged in lore speculation -- and come back next week when I tackle the Alliance side of politics and where they're headed come Cataclysm.