Zombies

In Thriller Barque, there are a variety of strange creatures that inhabit the island. The majority of them appear to be Frankenstein monster like creations. It is currently unknown what exactly their true nature is however a common theory until proven otherwise is that they are the creations of Dr. Hogback.

Cerberus


Cerberus is a three-head monster as seen in chapter 444. However, this One Piece version of the Cerberus is very differant then the common one from the Greek mythology. The Cerberus' body is armored and snitched, the heads are tatooed. Except for the right head which appears to be a fox, the Cerberus' heads appear to be dogs.

Nami, Usopp and Chopper encounter this beast after being trapped at the bottom of the moat where they'er are bunch of skulls. They fleed from this beast after it chased them, they hid in the tree from the beast.