You know, Archdruid
Shade: He constructed a World Tree without the blessing of the dragon flights, causing a tree that is warped and corrupted enough that it's being invaded by harpies, grell and grelkin, and corrupting the furbolgs that are supposed to be living happily on it. A tree that invites the invasion of satyr -- and the satyr are referenced in the War of the Ancients trilogy as being products of Sargeras, warping some dude with a god complex.
Silithus? He defended Silithus once, yes -- and watched his son ripped apart before his eyes in the process. That broke him. He shattered the Sceptre of the Shifting Sands, the key to opening the Gates of Ahn'Qiraj, when the dragon flights asked him to keep guard over it in the event that the Qiraj returned. He said he was done with the dragon flights and done with protecting the place.
His last words upon leaving the scene were as follows: "My son's soul will find no comfort in this hollow victory, dragon. I will have him back. Though it takes millennia, I will have my son back!"
You want to know what he's doing with the morrowgrain? He's trying to find a way to use it to bring his son back from the dead. He may have been a "leader" at some point, but after the War of the Shifting Sands, everything -- and I mean everything -- that man does is somehow related to his son's death.
... well, at least, that's what I'm putting my money on.