Blue Leg Hermit Shell. With a Worm in it instead.

[Choas]

It is about 1 to 2 inches long. Body was like a clear but The legs were White. It had these White things coming out it sides kinda looking like legs. Is it harmfull. It crawed out of the shell and went to the Live Rock.

 

[dskidmore]

It is quite likely that the hermit abandoned the shell or died, and the worm moved in afterwards, rather than the worm being responsible for the hermit's death. There are alot of beneficial detrivores that live in live sand and live rock. Unless you see prized possessions getting eaten, don't worry about it too much.

Good luck identifying him. Just out of curiosity I'd still try that.

 

[Fluff]

Sounds like a common bristleworm to me and is most likely, just checking things out or cleaning out the shell from the previous resident. I wouldn't worry about it.