Una and the lion, from Spenser's Faerie Queen
You were never masters, but friends. I was your friend.
I loved you well, and was loved. Deep love endures
To the end and far past the end. If this is my end,
I am not lonely. I am not afraid. I am still yours.
— Robinson Jeffers, The House Dog's Grave
Ah, the loyal, lovable, non-human friend. For whatever reason these dutiful companions will follow their (usually) human master just about anywhere. Sometimes it be magic, other times merely loyalty. In any event, everybody loves pets that know how to kick ass. Subtrope of Interspecies Friendship
This trope is so common that it's seldom used in a purely straight manner. Usually it subdivides into one of the following tropes: