Hello! If you're not familiar with first-person, grid-based dungeon crawlers then it's definitely worth taking a quick look at how some different popular ones play :
If your game is close enough to any game above you'll be fine, the mandatory features being walking in first person on a square grid and some sort of "life bar" and ""combat"".
Combat can take place on a separate layer from walking so it can be whatever and doesn't have to take place in first person or on a grid.