Shade of Glenicae  

Definitely part of some script. He spawns at the bridge after a Green Legion Commander shouted "Move out! We shall teach those weaklings at Crescent Reach that Dyn'leth is their true master." I'm assuming the group of Green Legion mobs starts to path towards the bridge and the Shade spawns when they approach.
As the force neared the bridge the Shade shouted "You shall not pass, return to the pit you came from, and tell Dyn'leth that I will not allow such attacks." The Green Legion force then began to path back towards the Centaur area and after a period of time the Green Legion Commander shouted "Halt! The dragon does not follow us. We are safe. Rally here"