I'm trying to learn how to play and for my character I am making a backstory to where her mother dies of a disease that slowly takes her energy/food, causing her to grow thinner and thinner till she passes. Am I allowed to just add that or do I have to use a disease already in the game? I don't have an edition yet but I want to start on 4th since I heard it's more user friendly for beginners.
In D&D, anything can happen. The books are there to be used as tools to help push your game forward, not to limit it. There are a variety of times, places, and reasons to stick faithfully to them simply because they are (hopefully) well-made, well-thought-out, and save you a lot of time and potentially headaches, but they do not necessarily define the entire game.
Nowhere is this more true than in our characters’ backstories, both PC and NPC. There are very, very few rules for these—because we don’t need them, they would only get in the way. Weird, exceptional diseases are a mainstay of the sort of fantasy literature that D&D is based upon, and therefore a perfectly reasonable thing to include in a backstory. You don’t need a book to tell you that.
What you do need, on the other hand, is for your group to be OK with it. Every group is different on this kind of thing, and for that matter, every campaign the group plays may be different as well. If playing in Dark Sun with die-hard Dark Sun fans, maybe it’s very important that everything about a character fit very neatly into the world, to increase the immersion. If playing in a setting your group has just made up, with only some of its details fleshed out, then adding a new detail may be quite welcome. In a different group, it is the custom world that is someone’s baby and they won’t be comfortable with you messing with it, while being blase about what is done with an official setting. It all depends on the people you are playing with and the kind of game you are playing.
So ask your group about it. In D&D, the DM generally gets a lot of authority about these kinds of things, but I think it’s good to discuss with the whole group. They may have additional ideas that help you, they may have concerns that you’ll want to address, and so on.
In a typical game of D&D (just about any edition of D&D proper) the division of labor/authority is approximately this:
- The player is responsible (almost always) for determining what the character does and (during character creation) some of what the character is.
- The GM is responsible for what the world does and what the world is.
So strictly speaking, character backgrounds are at least within the authority of the GM to veto, if not often within their responsibility as far as determining what the backgrounds are. But that is speaking very strictly, and usually only a concern if the character background is introducing new things into the world background.
It's also very close to the character, and many GMs allow latitude for things touching on the character background even if they do introduce new elements to the game. All GMs are different and have different tolerances for player input, but many GMs welcome players who bring their own ideas for things related to their characters into the game... as long as they're consulted first. The reasons for that consultation include:
- The world background is, after all, the GM responsibility, and he or she may have some reason that such a thing clashes with their background (that they may or may not be willing to explain)
- Most GMs don't like total surprises,
- Most GMs, if they are welcoming player input, want to know about it so they can use it
- Aside from all that it's just polite
The upshot of all this is, you should run your cool idea past the GM. They are the one with the formal authority to say yes or no to an idea like that.