I never thought I'd see such a thorough tour of hell ("Nightosphere," yeah, we know what they mean) done as a half hour special on Cartoon Network. It was funny, but it was
more a showcase for the incredible imagination of the staff. Great animation on all the demons. I especially liked the part-Miyazaki part-Bosch demon bus.
BTW, here's a rundown of the swords Finn uses, which was good for me because I could never remember when he looses one sword and retrieved another.
http://adventuretime.wikia.com/wiki/Swords