I just did this. I'm amused. Grave Shackles doesn't hold them down at all though. They did beat me up down to 500hp from 1500 (running too much around made some disengage). But I did get 1000 rep within a few minutes.
Creepy Green Skulled Crabs
Not so shackled
+200 rep a piece x 5 sand crabs = +1000 rep for me!
Thanks for the tip, cnnoi33. I'm amusing myself some more with these little guys.