Gotta go with a classic, author-san: Fenrir.
Since this isn't a Chinese novel, I'm guessing "Little Grey" doesn't suit.
Knowing Jack a little bit, he'll probably go with Mr Big Slashy Bite
thanks for the chapter, wolf name should be Nightingale if female, cause Death comes on swift wings when Nightingale sings. if the wolf is male, which I hope it isn't. it's name should be Sirius for the wolf star