Now that we're finally ready to start drawing the dungeon, it's time for a last essential part: the gimmick.
A gimmick is something that defines your dungeon. It's a mechanic that caters to the player and usually sets your dungeon apart from the others.
It can be as simple as 'straightforward monster-killing' to a more complex puzzle or trap.
Your gimmick can tie into your goal and theme and it helps if you think about the aspects of them, but it doesn't need to. Sometimes, the gimmick is the goal.
As my own dungeon is made of glass and it's the ruins of an ancient settlement, you can see the clear route of having a puzzle using the intrinsic qualities of glass. Glass can be seen through, but it also reflects. This means it'll probably have some reflection puzzles but why stop there? What if the whole dungeon was reflected and you could switch to the mirror version?
As you can see from my example dungeon, the gimmick sometimes already shapes the dungeon, as the mirroring means that my dungeon will be largely symmetric.
Multiple gimmicks are possible as well. You might want to ride steaming jets with a mine cart in a volcanic area for example.
Examples of gimmicks:
-plain hack 'n slashing
-the dungeon is the boss
-weakening boss by using items
-big moving puzzle dungeon