From the Gamesradar site:

"Fiona's four-legged companion proves essential to progressing through the game."

"Fiona can be seen hiding from the castle's resident looney-tune and persistent botherer, Debilitas (physically she's no match for the lumbering brute), while the advantages of befriending a hound are clearly evident as Hewie's killer animal instinct can be seen going to work on Debilitas' ankles."

Well, we all have our own little "Debilitas" don't we? SHOUT OUT to Hewey!