(Okay, this one really is a tease....)
Thrall had stood at Alcor's side for decades while he waited for him to die.
Maybe he had another twenty years to be patient, perhaps only ten. It would certainly have been less if he weren't under direct orders to protect the King of Eferem from any direct attack. They came too, for Alcor was not a popular king, and each time they did, Thrall resented having to protect the corpulent waste of skin, just as he resented having to keep silent and not tell his master precisely what he thought of him, in extensive, thorough detail.
The only thing that he could do with any impunity was hate, and Thrall made of it a work of art. He threaded it into his aura and projected it, and as the years passed, he worked on the subtleties of his hatred, growing and nurturing it with infinite care. It was his masterpiece and Alcor didn't even realize what it was, just as he didn't know what he'd made the grand mistake of trapping all those years ago. Thrall would make sure that he regretted tricking him into coming here. He would make every last soul in Eferem regret it with their last dying breath.
Because of his hate for his master, he thrilled when the little battler killed the prince and escaped with his woman, for all the infant was weak and not of his hive. He luxuriated when the king's man turned traitor and joined the enemy. He rejoiced when Alcor's generals were slain and their battlers banished.
The rage those events flooded Alcor with, the fear and hate they caused him, were what finally gave Thrall his grand idea. He could wait as he had been for Alcor to die, doing nothing more than what he was commanded, or he could cause his master to be destroyed without ever even touching him. The choice was a simple one.
So Thrall the battle sylph stood at his master's side and overlaid the man with his hate, slowly, subtly, driving Alcor's own paranoia and hatred, patiently remaking his master into a madman bound for war, and Alcor had no idea it was happening. There was no way he could, after all.
Alcor had no idea what he had in what he thought was just another battle sylph.
And Thrall had no reason to feel anything other than hatred.