The enemies are mostly new, but with a few from the Jade Passage thrown in. Since you're down to a party of two at early-to-midgame power, it's a hell of a fight just to keep everyone on their feet. Minwu is still a white wizard of some repute, while Scott starts with Fire, Blizzard, Thunder, Cure, and Life -- although everything but Life is at too low a level to be really helpful.
Borghen: Now we have all eternity together!
Josef: Borghen! Hmph, what a surprise... Alright. It's about time I settled your hash!
Borghen: Die here and you'll come right back! I can kill you until the end of time!
Josef: What!?
Borghen: Yes, the immortal body I've so longed for is mine at last!
Minwu: Careful... he's undead.
Scott: Borghen, you traitorous dog!
Josef: !?
Everyone teams up against Zombie Borghen. Since this is Final Fantasy and Borghen is an undead creature, the most important character in my party now is the white wizard.
Cure!
Borghen paralyzed Minwu to stop him from doing that anymore, but a Borghen retread is still just Borghen.
Minwu: So you're here too, Josef.
Josef: The prince of Kashuan! I heard you were mortally wounded in Fynn...
Scott: I was... and you?
Josef: After fighting Borghen, we fell into a trap he laid.
Yeah, I still have a lot of questions about that whole scenario.
Josef: It was a sorry way to go, but at least I helped those kids escape...
Scott: So you were also with them when--
Josef: And I don't regret a thing. They're young, but they've got spirit. Now, can either of you tell me where we are? Aren't we supposed to be dead?
Minwu: We think this may be the passage to Hell...
Josef: Jade!? The passage they say the beasts of Hell used to enter the world of the living? What are we doing here?
Minwu: There may still be some task for us to do. Something left unfinished...
Josef: An unfinished task, huh? Then we'd best finish it!
Josef, too, is exactly as he was when he left the party. While he was a fine fist-fighter against early monsters, he's even more fragile than Minwu now.
Since all of these party members are from before I really got anyone's Agility up to survivable levels, any little bit of armor helps. Thief's Gloves increase Agility (and thus Evasion) rather than being so encumbering that those stats drop, so that's a double-bonus.
Battles are still quite difficult -- probably about as difficult as the whole game would have been on the NES, haha. Josef adds a little more offensive power to the group, but he's so fragile that Minwu spends most of his time healing him.
On the upside, winning fights here nets you some mid- to endgame-level items. Check out the boost from that one weapon upgrade!
Totally worth it!
My favorite part of this quest is the sheer number of monsters who can effortlessly partywipe you. Glasya Labolas is one of those.