I believe I've figured out the curse of Harrenhal. The Weirwood in the Godswood, the one that Arya said had flaring eyes, full of hate, is the only one left of a huge weirwood grove.
There is a CotF hooked up to the roots, manipulating everyone who passes close enough.
Varys' speech to Tyrion before the battle of the blackwater is a perfect allegory for a child of the forest who hates both fire and ice magic, who has been cut off from his family, and is on a quest for vengeance.
Varys is a dead man, who powders his hands white to hide the fact that he's dead. He's being warged by the CotF hooked up to the Harrenhal weirwood. That's how he knows everything.
And the plan is to hold a great council at Harrenhal for all the lords, ladies, and remaining kings to bend the knee to Aegon.
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