I was told it is frogspawn, think I got a bigger pick - will post now.
Is it dangerous?
Hi Tobes - it is indeed a hammer - the shape of the tentacle end looks like "thor's hammer" ;-) (ending in a "t-piece" shape).
They are not "dangerous" as such - BUT they can give any other coral a "nasty sting". Possibly killing a part of the other coral. My torch-coral's tentacles stretches out nearly 8cm long, to "sting" a neighbouring coral. I had to move the corals away as well....
Another thing - this just goes to show the "inappropriate information" that people are sometimes given at some "shops".....
Even though the care of the frog-spawn/torch-/hammer-coral are all the same (mostly) - it could just as well have been quite different, and different care should be given....