The players in my weekly D&D 4E game have always danced the fine line between chaotic good and chaotic neutral, having been effectively powerful sources of good or at least self-serving in the world. They ended a war, stopped a major drug trafficker, helped open trade routes to another continent.

Lately though, they've been more and more willing to accept help from and make deals with less and less savory characters, including kidnapping human subjects for an amoral scientist working on a cure for an addictive drug, aiding a friendly and helpful demon encountered there get revenge on an ancient demon-slayer, and then gleefully accepting the praise and adoration of all the demons in the city who celebrate them as liberators.

When the archer thought it was a perfectly good trade to shoot a dozen orphans in the face to add bonus damage to her bow, and the rest of the group agreed and fought off the paladins who crashed the party, I felt it made sense to officially label them Chaotic Evil, and they agreed.

Now, after helping the main demon open a hellgate (to visit his family, bring his friends here to this newly liberated city, etc) they are exploring hell as honored guests and celebrities. First they had a snowball fight (because you have to), then they found some old foes in the lake of boiling blood they wanted to pick a fight with (and lost, releasing the soul of a pissed-off kenku assassin back into the world). Now I'm trying to figure out what else they could do to kill another session until the vacationing group members return.

I've based my hell on Dante's inferno, with rings and such, adapted only slightly for the D&D setting. They've got a demon entourage to protect them (mostly) from ending up stuck in hell, and they're too useful to the demons (much more chaos to come in the material plane) to be betrayed by them yet.

TL;DR - What are some fun and interesting skill challenges or combats I could put my party through in Dante's Hell?