I wish it was more rare. I had dreams about that damm thing and my finger still hurts. It's embarrassing to tell your co workers you were stung by a worm and that's why your finger keeps bleeding when you type.
That thing was so freakin gross. I have never seen one that size before in my life, I really never believed they existed, I don't think I will sleep for a week.
I don't think it would kill a fish on purpose, but if it rubbed up against one of my sleeping seahorses, the sting from the bristles might be enough to cause death, or to open the door for bacterial infections. I have a ton of small ones, and only noticed this guy because I was rearranging the rock. Never seen anything like it before ever. Must have been with me for some time.