There are no spoilers for any referenced series in this post. So don't be afraid I'm going to ruin something on accident.
I saw Avengers: End Game over the weekend, and while there is a lot of content in that movie that I'm still digesting it also has me thinking again about endings, and how necessary they can be in a way. Endings have value. They give us closure. They bring everything to a head. And they can, in a lot of ways, help us with all sorts of things. Today I want to talk about endings, and why you may want to have one in your game.
Anime vs. Cartoons
Growing up I always liked anime more than cartoons. I should specify that I liked certain anime. I preferred shows like the various Gundam series over things like Dragonball Z, not because of any inherent quality or trend. But the Gundam shows had a determined length (generally about 52 episodes) while DBZ goes on for some 290 or so episodes. It took me a while to realize that, but it is there. The Gundam shows ended. The story arcs came to a conclusion. The window into that world closed. Other things? Not so much.
The Dangers of Not Ending
You can see the dangers of not ending in a lot of shows. There is even a trope for one danger - Jumping the Shark (warning: TV Tropes link.) The second big danger - which leads to the first in a lot of ways - is power creep.
As a show, series, or any story continues you need to continue showing growth and progression. The next big bad or arc has to top the previous one. There are ways around this, but they're very hard to execute well on, in part because how does something that only threatens a small group of people really pose a challenge to a group of people who just saved the world?
You can also see this in D&D just with how things progress. Per dndbeyond, most campaigns end by level 10. Without context, this seems weird since D&D is generally considered to level cap at 20, but if you look into the game it makes more sense. Above level 10 the players can ignore more and more of the game. You start running out of "regular" monsters on the players levels, and instead are left with the type of creatures you expect as an end game threat. Considering D&D 5e is balanced around a lack of magic items, but DMs tend to give them out, it's not even unreasonable for a game to end around level 10-12 with the PCs getting an iconic red dragon fight.
And I can tell you from experience that if you go much further than 10 - such as with the Rise of the Dragon Queen story arc Wizards released - the PCs will be killing multiple adult dragons.
Just what do you do when fighting an adult dragon is no longer "an exciting fight" for your game? There's not many places to go while maintaining tension. Not to say you can't. Just, it becomes harder.
The Benefits of a Planned Ending
So if the danger of not ending is power creep and jumping a shark what is the strength of a planned ending? Quite the opposite. If you know you're going to end your game with a big fight with a dragon - or a shootout against the whole police department downtown - then you know about where power wise the game is going to end. Which means you can ramp up to that power.
You get the ability to ratchet up tension, plan out segments, and work things to get to that point. You don't need to worry about "and then what?" because there is no afterwards. Surviving PCs get an epilogue, and otherwise that window into the world is closed.
A Complete Emotional Arc
The trick to an ending is to deliver a complete emotional arc. This is closure, and it should be near complete closure. PCs should have a chance for their personal journeys to come to an end. Major questions should be resolved. There shouldn't be much left in the way of questions - beyond "and then what happens?" obviously - because the story should answer those questions along the way.
A Means of Focus
Finally, having a set ending gives you impetus to focus. When you have no planned ending it is easy to wander and dither around. With a set end to work to, you don't have the flexibility to wander around. And so you focus the story on what matters. Which in turn makes it a lot stronger.