So, the little important thing BS mentioned before ToM, that will play a huge role, but we apparently didn’t notice or discussed and BS couldn’t really remember in what book it was introduced, was the Ashandarei as a key, or?

Of course we discussed the Ashandarei and why it was given to Mat, though I agree that probably no one explicitely stated that one can use it as a device to open a door to leave Finnland and that this was the fulfillment of the wish (though think it would have made a bit more sense if the Ashandarei was at least made of bronze..).

Or was it the nightmares in TAR, which Perrin used to defeat Slayer?

Or something else?