I think another spectre from the past is definitely the memory of the Wolfbrother Noam from TDR, who actually lost control. In TDR, ch.9, Perrin already fears that he might also end like that. In TGS, ch.17, this thought returns:
"And yet, that rage he felt when he fought ... that loss of control. It worried him, more and more. The first time he'd felt it had been that night, so long ago, fighting Whitecloaks. For a time, Perrin hadn't known if he was a wolf or a man. And now —during one of his recent visits to the wolf dream — he'd tried to kill Hopper. In the wolf dream, death was final. Perrin had almost lost himself that day. Thinking of it awakened old fears, fears he'd shoved aside. Fears relating to a man, behaving like a wolf, locked in a cage."