Kowl is depicted as a small flying creature capable of speaking. His wings are not unlike large ears, and he has the overall appearance of something akin to an Owl mixed with a Koala, hence his name. It is mentioned that there aren't many members of his species left, and most of his relatives are dead.
Kowl is colored melon, with yellow eyes, a purple beak, and a rainbow-esque pattern on the inside of his ears.
He is something of an acerbic, sarcastic character who is a constant companion of the members of the Great Rebellion. Kowl tends to serve as comic relief as he is often cracking jokes and making slightly rude, piercing observations about the events unfolding around him.
He is sometimes portrayed as having a cowardly side, not unlike Cringer. In his first appearance during The Secret of the Sword he joins Cringer in hiding under a table while a battle takes place.