Ysondre

Ysondre was once one of the four Dragons of Nightmare, but has been freed from the Nightmare's taint.

Dragons of Nightmare
In recent times, Ysera's most trusted lieutenants were warped by a dark new power within the Emerald Dream. These wayward sentinels then passed through the Great Trees into Azeroth, intending to spread madness and terror throughout the mortal kingdoms.

Once one of Ysera's most trusted lieutenants, Ysondre had gone rogue, sowing terror and chaos across the land of Azeroth. Her formerly beneficial healing powers had given way to dark magics, enabling her to cast smoldering lightning and summon the crazed spirits of druids trapped within the Emerald Dream to aid her. Twisted and insane, Ysondre was bent on unleashing vengeance upon the mortal world as if Azeroth were the force behind the Emerald Dream's corruption.

Cataclysm
Now, Ysondre is the last of the former Dragons of Nightmare, and although she has been saved from the nightmare, she states she can never return to the green dragonflight. Emeriss and Lethon are already dead, and Ysondre helps players kill Taerar during a quest chain in Feralas.

Trivia

 * It is interesting to note that when shouting out their challenges in their respective zones, the other dragons' quotes had words with negative effects ("DISEASE", "NIGHTMARE" and "SHADOW") in capitals, while Ysondre's word "LIFE" bore a strong meaning to druids and dragons alike.
 * While the eyes of Lethon, Emeriss and Taerar were wide open, Ysondre's eyes were closed.