So that’s a pretty wide topic. I would first categorize the elements you mention as follows:
- Easter eggs (like references to previous titles):
Most of them are based on our general knowledge of the brand. It comes from our own playing sessions of the old games (I personally really liked the character of Al-Zahir), from little stories shared by veterans devs, or from what the players like to share because they find it fun, compelling, etc (Jorgensen family that NEEDS to be present in every game, and references to their forefathers). We still have some documentation of the old games that we can have a look at in case we want to be precise and not rely only on memories.
- Intertwined stories of the game
The easiest way to answer your question on that point is to take one example. Here I’ll talk about the creation of the Enbesan region and the many storylines that develop in the same world and through multiple islands (I think you mentioned in another question having played Land of Lions right? 😉 )
To keep track of everything, we used different types of documents.
1/ Timeline document
To make sure that all the narrative will fit together (storylines, characters, but also visuals on the islands), we need to build a strong world for the region and document it. This acts as a guideline for all the content created.
To do it, we first sum up all elements that come from game design (importance of water through irrigation, science development with the scholars…) but also our narrative wishes (conflict modernity / tradition, “what is an empire?”…) and find also historical references that could spice up the world building, based on the real region we chose as inspiration.
Out of it, we build a timeline. It contains all kind of stories we could think of: ancient myths, religion switches, important characters, constructions and destructions.
This timeline is one of the documents that will make sure no anachronism will appear later in our quest development.
2/ Islands design document
As we wanted to have quests islands, we first had a brainstorm with the level art department about what could look cool.
Based on the setting (desert/savannah), fantasies (old ruins), the main themes of the DLC (water, research), we came up with multiple ideas and merged them into 3 big ideas to make the 3 quests islands of the DLC. By having already some keywords, some visual and historical references, we had a good idea of what those islands would look like and what kind of stories would happen there.
Then we updated the timeline, adding what happened to each island at each era, what role it played in Enbesan history, what got constructed and destructed, for what reasons, what characters lived there… We also created separate islands documents mentioning what ruins and buildings lay there, what’s their position, when was it built, architecture style, what vegetation…
This island document is the core document used to develop each questline. I used it a lot when looking for a character to add to the questline, when looking for a ruin or any building that could help telling the story I had in mind. It’s not only a way to ensure all narrative elements will fit each other, but it also acts as a library of ideas to bring the quests forward. It is also a great way to communicate with the Level Artists the direction, look and feel and important landmarks of each island.
3/…. Expansive Spreadsheets !
And yes, for the quest design and their implementation, as they’re interacting with each other and update the islands visuals, we have to establish strong documentation. The hardest part was to keep the little speech bubbles (those that appear upon clicking a game element) on line with the quest development (so that they don’t contradict each other), make sure buildings appear and disappear on time, etc.
For that, I built a huge spreadsheet tracking the state of each game element for each quest state, and their corresponding speech bubble content. It was then easy to keep track of all of it, as it was like a chronological map of all game content based on quest progression.
Spreadsheets also helped a lot to communicate with Level Art, as they had to build each game element in the engine and give them a unique number for me to assign triggers to them.
Sorry for the long block of text 😊 I hope that answered your question!