Two adventurers enter the dungeon for their goals, one a warrior, one a mage.
The theme of duality is present through there being two characters, that need each other to survive, if one of them dies it’s game over, and in the second part they gain abilities that compliment each other.
It was also going to be present narratively, as those who built the dungeon failed due to their sins, while the heroes are driven forward by theirs, but I wasn’t able to satisfactorily place it within the time limit.