I didn't really understand the leveling portion other than:
XPTotal & LevelUp = Level+7 - XP
However when you hit level 10 the manual says you must create a new character as an assistant or etc. But can you not just keep leveling? While this will indeed make them stronger you can scale monsters and add custom powers for new levels if you wish. Is there any reason I cannot do this and not break the game?
You could keep levelling, but the game starts breaking down. You start running out of moves that you can take and you rarely ever fail rolls because your stats are all in the positive. The engine runs out of steam and the game starts to be boring.
So you can, but you would have to start houseruling lots of bits of the game to make it work. For a lack of moves, you could either add more multiclassing options at level-up, or you could go big and add a whole new tier of level 11+ "epic" moves for each class. (You can write new moves one at a time as each new level is gained though, so you don't have to write a whole tier all at once.)
For bonuses, I have no idea how to fix that: making things harder mathematically doesn't actually work very well in Dungeon World, and otherwise there's no effective way to make the 10+/7–9/6− continue to work and trigger GM moves often enough keep the game rolling. Remember, the GM doesn't even get a turn to say what happens next unless the players give it to her, either by looking to the GM for what happens, or by rolling a miss. If the players never miss, that's half the GM's input into the game gone, and the campaign's momentum with it.
So yeah, you can, but at some point you're playing a different game design-wise, and you're in unknown design territory, piecemeal crafting a brand-new game without any useful guidance from the text of Dungeon World. Go for it if you like! But be aware of what you're getting yourself into before you go for it.
First, make sure you're not accidentally robbing yourself of 10th level entirely. You said
… when you hit level 10 the manual says you must…
But that's off by a whole level: you only follow the Beyond 10th Level rule when you are already level 10 and you would advance to 11th level. I've seen numerous posts scattered around Dungeon World discussion sites where people make the mistake of following this rule as soon as they hit 10th level, which does make a character's career significantly shorter than it should be.
With that out of the way, it's worth taking another look at the existing 10+ level-up options. Like most parts of Dungeon World, they contain way more than they appear to at first glance. I don't know what your particular motivation is for wondering about continuing past level 10, but as this is a pretty common question about Dungeon World, I'm going to cover all the bases and let the reader make the final evaluation with more information.
This one is pretty straightforward: you retire the character and make a new one. But note that the GM is still beholden to the GM's Principles when you make this move, in particular Be a fan of the characters and Think offscreen, too. Your retired character doesn't suddenly stop existing – they don't suddenly leave the game. They do, in the fiction, literally what the move says: the person retires from adventuring to a place where they are (relatively) safe from the dangers of the GM's moves. They are still in the world, and the GM is still required to be a fan of them and to think about them while they're offscreen.
As well, when you make this move, you still have to follow the rules: the move returns to the fiction. That means that when you trigger the move and choose retire, you have to, nay, you get to say what that looks like. Do you get given a title for service to the realm? Do you become headmaster of a school of wizardry? Do you found a new branch of the church in a new land? Do you settle down into a new dwarf kingdom under the mountains? What awesome thing does retirement look like for your character? You get to work with the GM to figure that out.
So what retiring means is your character becomes an awesome NPC in the setting. Retiring a PC to safety is your way to make one last big change to the setting. That's pretty sweet, and not an option to be overlooked.
You get a second character, your first stops advancing, and your new one gets to restart the whole rags-to-riches story again while your original PC keeps on being their awesome self. This may seem like a step backwards, but it's not: it's getting to have extra spotlight and more opportunities and ways to control the fiction.
If starting over as a 1st-level scrub seems like no fun, remember that Dungeon World is designed so that you can play with a mix of levels and it works just fine. It's even a rule to emphasise the point: when a new character comes into the party after your last character dies, you start at 1st level no matter what level your dead character was. I know lots of people doubt that would work, but trust that the game knows what it's talking about and that it does work. This ain't no D&D 3.x, where level disparity can be a huge problem.
So, consider the benefits:
You get to start with a 1st-level character over again. You get all the things a 1st-level character does when they enter an existing group: new questions from the GM that you get to answer and shape the world with, faster leveling because you're going to hit those 6− rolls and mark XP more than your fellow PCs will, new-to-you awesome moves that get to influence the direction of the game in ways that you haven't been able to with your last PC.
You get all that, and you get to keep your fiction-making juggernaut of a 10th-level PC. You can team up on an enemy all by yourself now, you get double the influence over the direction the game goes next, and you can be in two places at once. That is super-powerful, much more than the simple words "Take on an apprentice" might seem to be at first glance.
This has all the benefits of a brand-new PC, except that you keep a tonne of stuff from your previous class. Consider it the super-multiclassing move.
What do you keep?
That last bit is huge. Remember, the GM is rules-required to Be a fan of the characters. Being stingy about agreeing what is core to who your character is, isn't any part of the GM's Agenda and Principles, and a GM who's being a hardass about what you get to keep is not following the GM's rules.
You get to keep everything that makes you who you are. Are you a master thief, with your own thieves' guild, an influence-peddling racket, an infamous reputation for impossible burglaries, and basically own the kingdom with a web debts and obligations owed you? You keep all that, plus the moves that suit that identity, even if you suddenly develop an interest in enhancing your legend with the ability to turn invisible and use other spells useful to a master thief. That might mean you get to be a wizard plus the Thief moves Flexible Morals, Poisoner, Wealth and Taste, Connections, Escape Route, and Heist (assuming you took a bunch of moves with those among them, and those are the ones that match where you've gotten in life). You lose everything that isn't essential to who you've become, so maybe you lose things like Evasion and Serious Underdog because you haven't been known as a scrappy brawler since your early days.
Like I said, change class is the super-multiclass move. You get to keep a lot, a lot of stuff from your previous class, and then you get the fun of playing with a new class's toys all over again, while still keeping your best toys.
Yeah, you can keep levelling past 10, but the math and other intangibles of the game are designed around the 10th level cap. To best keep going past level 10, you can probably just keep playing while keeping an eye out for where the game starts to break down, and adjust as necessary when you get there.
And besides, this is a not-uncommon question. After all, to someone coming from any other fantasy game, level 10 seems really, really low! So the motive for asking this is usually just being not quite aware of just how good the level 10 level-up options really are. Take another look at those and consider whether you actually need level 11+ options, or if the game already has you covered.
I was reading Class Warfare by Johnstone Metzger and read a passage that brought this question back to my mind. The passage reads as follows:
You can also use this collection of specialties to allow characters to advance beyond tenth level. As long as characters aren’t gaining so many moves that players feel weighted down by them, it is perfectly reasonable to consider level 11 no different than levels 6 to 10. Once you gain a compendium class or two, you will have plenty of advanced moves to choose from once you pass level 10.
The specialties mentioned are essentially compendium classes. While I am not certain this side comment would constitute a 'rule-as-written' alternative, it is at least the opinion of that 3rd party dungeon world supplement author that compendium classes are a viable way to handle leveling up to 11 and higher.
