Brutor is a bull mastiff. He used to belong to the arsonists, but after being subdued by Bertie's sparkling intelligence and personality, he now accompanies Bertie, normally in an improvised puppy puppoose.
He accidentally let out some contained skeletons in the British Museum, which The Rangers had to deal with.
At the reading out of Bertie 's last will and testament, Brutor was revealed to be the designated heir to his former master. In order to properly carry on the terms of the McGuffingham contract and accept the inheritance, the dog was somehow given humanoid form and the power of speech, possibly through the intervention of the lawyers at Harkness, Harkness, Darkness & Sphinx. Brutor's new form was revealed to Sasha when the lawyers fulfilled her request to be present at the presentation of Bertie's enchanted sword to his heir.