Small Ferret is a ferret that was wit-bonded to an unknown human who he referred to as "Big Ferret". When "Big Ferret" was killed by Regal's men his dying wish was for Small Ferret to avenge him. To this end Small Ferret starts living amongst Will's belongings in hopes of getting close enough to Regal to kill him.
When Fitz attempts to break into the inn that Regal is supposed to be staying at in Blue Lake Town Small Ferret warns him that it is a trap intended to draw him into the open. He reveals that Black Rolf had asked him and other Old Bloods to assist Fitz and Nighteyes if they could.
It is suggested that eventually Small Ferret is successful in killing Regal and afterwards continues to live for some time with Chade Fallstar.