Martin originally planned a "deadly rivalry" between and Tyrion because they both fell in love with Arya Stark
The existential threat. Ice demons who raise the dead. The index’s entry is short, because they have no words, no mercy, no politics. Only silence and cold. Their weakness: Dragonglass, Valyrian steel. Their fate: Defeated by Arya Stark.
The central mystery of the index. Raised as Ned Stark’s bastard, in truth, he is Aegon Targaryen, son of Rhaegar Targaryen and Lyanna Stark. He is the union of Ice (Stark) and Fire (Targaryen). He is the hidden heir.