Challenge suggestions?

[takatohedgehog.livejournal.com]

So I've finally gotten up to the part where I need to start planning out my challenges for my MC to face. I don't read that many books where the MCs have to go up against challenges, but for the sake of NOT ripping off Harry Potter, I want to do something original. I know I want something to do with one of the rivers that cross through the Underworld (believe it or not, there are about five more than the Styx, but the Styx is the one that's more well known than the others), and I know that they all need to take place in the Underworld.

I want suggestions. Please help me out? I'm looking for challenges of strength, courage, wisdom, heart and mind.