Inferno on the surface.

It would be better to create a proper Inferno-themed map in the Dungeon.

That's also a good idea, because it's not very good as it is; it's your land, but there are no bonuses. The units aren't particularly strong anyway, so at least give them a bonus, +1 to speed will definitely improve their ability to clear out neutral creatures. And it will be much more playable on the surface.
It's a shame that this option can't be added to the poll anymore.