One spawned very close to my new cave on a new world I started, it's bloody massive and kicked me right back into my cave, got it the second time around tho. It dropped a pickaxe and a heart which I had no idea what it was for, but I do now reading this thread.
Yeah, the heart containers are great, I very nearly got my forcefield protected ass handed to me by two arse magicka mages, the only reason why I survived the sudden ambush was the three extra hearts I now have.
I get extremelly pissed orf everytime this happens, you don't expect a mechanic suit whizzing with raw electric power and crackling with forcefields you spent half a barrel of iron on to just pick its metaphorical nose while you're screaming in agony.
Needles to say, I considered nuking the spot to clean the taint of magic off of it, but it also happened to be the spot where I'm building, so I thought better of it.