Velen

Ancient History

 Millenia before the Warcraft game the Eredar were a people who lived on the world of Argus.  Their achievements brought them to the attention of Sargeras, the fallen Titan who originally led the Burning Legion.    The Eredar had three principle leaders, Archimonde, Kil'jaeden and Velen.    
 
Sargeras promised great magical power to the three leaders.  Archimonde and Kil'jaeden accepted the offer of power.  Velen however saw through the trick and realized that Sargeras was about chaos in a universe all about order.   
 
Velen's great gift, that made him a powerful leader to his people, was that  he was very good at prophecy. He received an answer from the Naaru and was able to escape Argus for Draenor.    
 

Rise of the horde

 
Velen had been able to foil other attempts by the Burning Legion to get at Velen and his followers.   Since Velen was so good at predicting things that would happen if the burning legion tried to attack them they did it differently.  The violent shamanistic culture of the Orcs revered their ancestors and lived side by side with the Dranei on Draenor.   
 
Kil'jaeden instead of directly attacking the Dranei instead went to the Orcs.   He went the shaman  ner'zhul disguised as the spirit of Nerzhul's wife and told him the Draenei were plotting against the Orcs.  Ner'zhul and later Guldan destroyed most of the Dranei civilization on Outland.   
 
Velen and the Dranei spent much of the next two decades in hiding before  other creatures came back to Outland.   
 

Burning Crusade

  
When Illidan, Lady Vashj and Kael'Thas Sunstrider came to Outland at the end of Warcraft 3 Frozen Throne it put many things in motion.   Velen and some of his Dranei mounted an attack on the Exodar.  The Exodar was the 4th wing in Tempest Keep, where Kael'thas would make his stronghold.    
 
He was able to take control of the Exodar and use it as an interdimensional vehicle to escape Outlands.  But some Blood Elves on the Exodar sabotaged it and caused it to crash land into the northwest cornder of Azeroth.  
 

Sunwell Plateau

 
Kael'Thas Sunstrider captured the Dranei M'uru and sent it back to the Blood elves as a means of curing their magic addiction. After his defeat at Tempest Keep and rescue by agents of Kil'jaeden he stole the Naaru and intended to use it to reignite the Sunwell and bring the head of the Legion into Azeroth.   
 
After players, with the help of some blue dragons defeat Kil'jaeden Velen reignited the Sunwell as a source of Holy Light with the sacrifice of the Naaru .  It cured the Blood Elves of their corruption.