The collaborative nature of the Era of the Dragon means that writers will work together to produce a cohesive narrative. To that end, it is important to understand the relationship between PCs, NPCs, and You. Your personal PCs are your way of interacting within the world of EotD, and the characters within that world have different designations with different considerations to keep in mind when writing your updates for the narrative. In general, the idea is to understand the other characters well enough to be able to represent them accurately and properly in your writing. Information on how to handle specific character designations can be found below.
PCs (player characters) are the characters created by writers for the sake of interacting with the world of EotD. These will ultimately function as protagonists and will require more collaboration than the other character designations. As protagonists, writers are encouraged to feature these characters in their updates, but do so with regard to the current events of the story and special regard to how the character(s) portrayal has been up to this point. If you would like to feature another writer's Primary PC within your update, speak to them ahead of time about it (whether major or minor). Discussing it ahead of time will prevent a plethora of problems occurring. Remember that this is a collaborative narrative, you don't have to collaborate with someone for every last chapter that you contribute, but doing so (in little ways if nothing else) is part of the charm of this experience.
Important NPCs (non-player characters) are the characters which have been created with regard to the plot. These characters are obviously created by someone, but their involvement within the story takes place outside of the protagonists' journey. They will intersect at points, but will otherwise be separate. Examples of characters designated to this group include antagonists, arc villains, non-active PCs, and more. The importance of "Important NPCs" can vary drastically, but the key is that they aren't active PCs, and they aren't mere background NPCs. When seeking to utilize these characters, just try to make sure that you don't contradict your fellow writers and that you are faithful to represent them accurately.
Background NPCs are basically one shot characters that won't appear again within the story. They are certainly eligible to become Important NPCs and even become PCs if that is desired, but otherwise they are basically nothing more than fodder for writers to accomplish what they seek to accomplish in their writing. Background NPCs should still be treated with diligence and respect however. Suppose for example you had an assassin that was designated to this category, that assassin should show competency in his/her craft. There is nothing wrong with that same assassin dying within the same paragraph that he/she is introduced in, but have it make sense, that's probably the biggest thing for background NPCs - handle them in a way that makes sense.
All in all, the goal of EotD is a collaborative narrative. This means that your personal PC will be used by others. This means that Important NPCs that you create will be used by others, and that people may borrow the background NPCs that you make. Be respectful of the creations of others when you utilize them and make sure that you aren't contradicting anything that has already been written or is planning to be written, communication is the key for that. Read what everyone else writes and try to understand everyone's characters as best you can. Try to be understanding if someone doesn't perfectly match your personal vision of your characters, but if someone is simply portraying the character poorly then discussion can be opened up about what to do.