Baskerville

Baskerville（バスカヴィル, Basukaviru), also known as the Black Dog (ブラック・ドッグ, Burakku Doggu), is one of Alucard's familiars in the Hellsing series. Its form varies, but it usually appears as a large dog with shaggy black fur, multiple red eyes, and a large, fangy mouth. It usually emerges from either one of his arms, almost serving as some sort of extention for his selected limb.

Baskerville appears to be one of Alucard's favorite familliars, since he tends to use it against opponents he considers challenging.

The name "Baskerville" is a reference to the Sir Arthur Conan Doyle novel, "The Hound of the Baskervilles". Its name was revealed in Volume 9, when Alucard summoned it against Walter.

It seems to be able to absorb powers for itself as in the case with Luke Valentine, as Alucard states that it wasn't a complete waste to feed him to his dog, after observing it's speed and movements similar to Valentine's.

In the anime, after Alucard is killed by Incognito, he returns from hell in the form of Baskerville.

In Hellsing Ultimate, its eye makes out the shape of the word "shit" as it devours Luke Valentine.