There were an awful lot of plots, even for something with four parts. I think the shell was some cursed thing that belonged to the haemovores or to Fenric's treasure? And lol, yes, there was a random glowing pot, which was also Fenric's treasure? But then the treasure was kind of not very important? Or something. Definitely something. :P

Haha, yes, the Evolved Difference Engine. It must be a very special ENIGMA machine if they can use it to Rosetta-stone random alphabets in addition to decrypting ciphers of known alphabets. :P