Hello Everyone and thank you Zhaleskra for the interesting topic.
I am currently GMing a Kingmaker campaign which by its nature is a sandbox design with an emphasis on exploration and the PCs determining the pace of the adventure. However, I have heavily modified this knowing that my players still prefer a little GM direction thrown into the sandbox.
I look at an adventure design in terms of layers:
- Layer One [Set Encounters]: These are based more on position and that if the PCs venture into a specific place, they will encounter something specific that is unlikely to react to change although it may in and of itself gently evolve. They are effectively fruit waiting to be picked by the PCs. The important thing here is that these may be experienced by the PCs or not; completely dependent upon what the PCs do.
For example:I have the awakened, giant dire boar Tuskgutter sitting in the forest waiting for the PCs to eventually turn up. He's an evil brute of a bastard doing his best to impersonate Jaws. The PCs currently are giving him a wide berth but as the months tick away, more hunters die and their names marked on the side of Oleg's trading post.
- Layer Two [Joined Set Encounters]: These are similar to layer one except that several of these set encounters are inter-related. Interacting with one will generally affect another or direct the PCs to another set encounter (with the direction being followed or ignored by the PCs). The important thing here is to not have these joined encounters requiring a particular order but instead vary depending upon the order that the PCs interact with them.
For example: the classic case from the module here (which I will disguise so as not to spoil) is where a clue from Encounter A leads to investigating Area B which in turn leads to making a deal with NPC group C. While the PCs are not forced to encounter these in that order, there is a natural progression that is easily followed if the PCs are trying to chase down a particular McGuffin.
- Layer Three [GM Bombs]: These are the instances where I as the GM deliberately throw a situation at the PCs either prompted by their actions or activated according to a timeline I as the GM am reacting to. This timeline however is very GM-centric rather than PC-centric. It is effectively the lever I use to pace the game so that each game session will have a productive start and an interesting finish. It is where I throw a cat amongst the PC-pigeons and see what they do with it. Almost all dynamic NPC interactions are part of this layer.
For example: I engineer Professor Lorrimor to arrive at Oleg's trading post shortly before the PCs return there, knowing in all likelihood that they will help escort him to Ravengro while beating off some bandits that they have heard have recently set up on that particular road. There are some hooks that you know your characters are going to bite on.
(Of course if they don't bite then you try to introduce some alternative repercussions that don't overtly penalize the PCs but instead just logically extend from the situation). For example, I certainly wouldn't have had the Professor be killed in ambush in the above example but he may have been forced to return to Oleg's, unable to break through the bandit ambush.
- Layer Four [Random Stuff]: This is where I throw planning aside and make stuff up on the fly. It is not just a case of crafting new characters or scenes but also crafting new unplanned connections between all of these. It's when you see the PCs do something and then think, "wouldn't it be cool if this happened or so-and-so appeared unheralded or turn generic character A into character B's lover, ancestor, future murderer etc. I love as GM getting these off the wall ideas in the middle of a game and thinking, "bugger it, I'm throwing this in" and rolling with the completely unexpected; even if it has the potential to derail or invalidate a whole section of planning. I find that if the campaign world does not evolve in some unplanned way, I tend to both lose a little interest in the world as well as play things a little flat as a GM.
For example: I recently had the PCs dream/or have a nightmare where the players are momentarily given new characters to roleplay, in both attempting to foreshadow the events of Harrowstone prison as well as determine what actually happened in the final moments before the prison was burnt to a haunted husk. On the one hand, I'm handing the PCs some very valuable metagame knowledge with a reason for in-game access to it. On the other, I'm letting them define what actually happened rather than me just referring to backstory. The key now is me processing this new information to change and mould the haunted setting if and when the PCs actually go there.
I find that combining all of these layers, the players get what they need out of it and so do I as GM. They feel like their characters are important and have a logical impact upon and momentum in the campaign world and I get the enjoyment of seeing how they get themselves into and out of situtions as well as occasionally getting to play the "what if?" card.
Best Regards
Herremann the Wise