Nightstalker... let me just lay out a few facts before you reread Brienne's sixth POV of AFFC.
Sandor is a very tall man... probably only Gregor, Hodor, and the Greatjon are taller.
When we last saw Sandor in ASOS (near the mouth of the Trident, close to Saltpans and the Quiet Isle), he was left to die from a severe leg wound.
Sandor's horse, Stranger, is a nasty piece of work.
Sandor's nickname is The Hound... and besides his warhorse, the only things in life he has an affinity for are dogs.
Because of the abuse that Gregor heaped upon him, Sandor loathes knights.