Levels

[kcunning]

Give our dungeon stairs, and multiple levels to go to.

Change monsters per level?

[IanWitham]

Some rogue-likes give monsters and weapons a "level" where they are most likely to be found, but with a sort of bell shaped probability of being found on other levels, so you will generally only encounter easy monsters and worthless treasures on a shallow level, but with the small probability of encountering something surprising. That could be more interesting than "level 1 has slimes, level 2 has rats" etc.

[kcunning]

This is something I think could work. Every level should have something you can grind on... and something you should be running away from.