He's a Daedra, and Daedra don't die. He simply got banished back into his plane of Oblivion.
Or you were joking back there... Heh.
I don't know, it's hard to think of an easter egg thing to put into the game when you have almost 20 things like that as rewards for helping daedra. Maybe you find Herbert/Harold/Bob from FO3 living somewhere and he tells you he's been there for thousands of years, the lands of Tamriel and all the races evolved from the irradiated creatures of the time and Spriggans are his 'special' offspring.
I'd still like to see a lot of diseases which have phyisical effects, Mad Cow disease, Swine Flu, Chicken Pox, Bird Flu, Bee Mites, Minotaur-ization, etc. And some which have beneficial effects too, Mad Scientist disease, (Corprus was a good example to some extent, raised strength every day you had it), Wood Heart to raise endurance, etc, and of course the beneficial effects come with some not so nice things...
Stephen.