Stranger

Stranger is Septon's Sullon cat, and most likely his closest companion. He has been with the Septon since his elevation to Master of Whisperers, and follows Sullon about almost everywhere. Indeed, it's even been rumoured that the bond between the two is more than it seems. It is said he is descended from a breed of Dornish Snake-Hunting Cats.

History
Having spent most of his life with Septon Sullon, Stranger has become a staple about the Master of Whisperers, often moving ahead or behind his master.

An expert rat-catcher, its said that Stranger's talent of pouncing on prey unawares is second only to Sullon's, and indeed the two work together to an almost eerie extent, some theorizing that the two somehow communicate mentally.

Of course, that's all crazy talk right? All Stranger cares about is his food, his fish, and his master.

Encounters

 * Selenya Targaryen had a harrowing encounter with Stranger in the Sept at Harrenhal. He helped his master with a masterful analogy, and was rewarded by catching a mouse.
 * Septa Malora found herself trapped beneath the ball of fur while in the confessional with Septon Sullon. She was lucky to escape relatively un-furred.