Hell was not all that, really. For one, there weren't any windows in the labyrinth of stone corridors. It was also really stuffy. The air had no oxygen, but was filled with all kinds of poisonous or flammable gases, which, besides being bad for Jack's skin, didn't make it pleasant to breathe.
The heating was also a problem. Everything was hot. Way to follow stereotypes, right? Jack's mortal body was not really equipped to deal with this much heat, and if Jack wasn't the strongest, most durable fairy to have ever existed in the mortal realm, he would have died just from dehydration.
It was Jack's amazing cultivation technique, and the constant feedback from Lex, which made Jack's body much stronger than any fairy had any right to be. Crippled as he was without his fairy dust, the only thing he could rely on was his body, so it was a good thing it was so tough.
