[Everything] Who are your favorite GoT characters outside of the main story?

I've been looking into the histories of Westeros and everything and there seem to be some really interesting characters outside the main story.

Aegon the Conqueror and his sisters really interest me, especially the complicated relationship with Visenya. Brynden Rivers is probably one of my favorites (before he became the Three Eyed Crow).

Who are some of your favorite characters from before the events of A Game of Thrones?