[zepath]

If it's been done as the poster and Kristoffer O said, there should be little theoretical trouble in expanding the idea to include things like the demon realms and perhaps elemental planes (substituting the appropriate monsters for the fights). For the Inferno/elemental dungeons perhaps it would be best if they are accessed by ritual spells?

I didn't know this element of play existed in Dominions at all. Personally, I think its a wonderful idea and happy to hear its been implimented so long as the dungeons are dangerous enough that repeat visits will ultimately get you killed. Otherwise it could be abused. Perhaps a limited access element would be appropriate as well... dungeons are cleared out after a month of adventuring and won't be exploitable again for at least a few turns. It may also be fun to include increasing levels of difficulty for each forray into the dungeon as the adventuring commander delves further inside. For instance, imps and a devil meet you on your first step into Inferno while one of the Heliophagii will come to challenge a repeat visitor.