Give a piece of meat whenever you encounter the wolf/shadow creatures at the campire and eventually it will join you. It attacks enemies at the start of a fight. Also, don't forget to upgrade it at the campfire to make it deal more damage.
If you reach a certain area of the tower that seems overwhelming, return to previous areas to level up, collect new equipment, and earn some cash. You'll find that even just a single visit to a previous area may make you strong enough to take on the section you were stuck in.