Half-Human, Half-Crab

Here I am, inside a dungeon at the bottom of the ocean. Standing on top of corpses of fishes and monsters that have fallen down, surrounded by monsters that I see for the first time.

They're all humanoid. Very similar to a human except for a pair of extra arms coming out of their shoulders. And those are not hands. But claws like that of a crab.

And they can easily cut the bones of a monster easily with those claws. And unlike humans who only have one elbow on each arms, at least normal humans, they have several elbows. Some have five, and some have three. My guess is that the older they are, the more joint they have.

With those joints, even though those claws are on their shoulder, they can move them freely. And the more joints, the more versatile they are in their claws' movement. I think. I haven't seen them fight yet.