I don't know if "Challenge" is the word I'd use to describe the nether...See, here's the thing. You can't Esc, inventory, type, or anything when you're in a portal. And when you spawn in a lake of lava, 20+ ghasts around you, well...It's pretty much impossible. Literally. There was nothing to do but copy "/gamemode 1", and jump into lava, hoping I could t and ctrl+v in time not to die. I don't think challenge is the word. It's pretty much impossible in my eyes. I cheated to achieve that quest, and am never going back to the nether unless forced. I recommend at least giving the player a platform to start on in the lava made of cobble or something, and not making it so that there's so many ghasts right off the bat. Just my suggestion.