It’s impossible to plan for every white rabbit your party might chase. Faced with this daunting task, some DMs can fall into the trap of “railroading” their party through a series of encounters that hit certain narrative beats. This is not necessarily bad, but it can detract from player agency.
I think a big problem is that the game materials don’t really teach you how to sandbox. Most modules are presented in a linear fashion that naturally trains DMs to drag players through a story line. Sure, you’ve got tools to help sandboxing: random encounter tables, random loot tables, random weather tables. But these don’t create a cohesive picture unless you paint it on the fly.
How do you run a sandbox without being completely overwhelmed by the expansiveness? Let’s tackle this by dividing it into two sections: planning the sandbox and running the sandbox.
Planning for the Sandbox
Planning a sandbox means that you need to spend less time developing the narrative beats of your campaign. Rather, you need to develop a dynamic and world of NPCs that reacts to what the players do. Instead of one Big Bad Evil Guy (BBEG), flesh out a few factions that have competing interests. Place them in relative balance that will be tipped by the party.
Example: A powerful alchemy company has been moving into abandoned towers spotting the river. Their spread has been dampened by orcs roaming the territory.
Develop an appropriate number of factions based on the length of the campaign. A one shot might only require two different factions to generate a tension. More numerous opposition is appropriate for a longer campaign. If that seems daunting, you can always start with two factions and flesh them out as the campaign develops.
Remember that these factions should also have their own power structures. This allows them to adapt in response to what happens in the sandbox.
Alchemy Example: The company is run by a powerful wizard that enslaves duergar to mine potion reagents.
Orc Example: The orc matriarch recently died, and her three sons are fighting for control of the throne. Each commands a different tribe that they want to use to seize control of the orc kingdom.
Ideally, you develop these factions by pulling threads of each player’s backstory, so that they have character motivations to execute. However, you don’t need to create all this from scratch. Check out the Monster Manual, Volo’s Guide to Monsters, and Mordenkainen’s Tome of Foes and you’ll often find that there’s already a series of reflavors that you can adapt to your setting.
Running the Sandbox
The problem most DMs encounter running the sandbox is that they put one piece of bait before the party and hope they go for it. When the party invariably decides to go another direction, they panic because they have nothing prepared and they’re “off script” in the campaign.
The secret: you don’t need to be “off script” to run a sandbox. Just make the test multiple choice instead of fill-in-the-blank. Give the party enough spinning plates and they will feel like there are things they have to get done.
Remember those factions we prepared? Just think about what they would do in any given situation. Use those motivations to prepare encounters that tell the story of those factions.
Alchemy Examples: The company is dumping chemicals in the water that affect the nearby town: hallucinations, elementals manifesting, sudden telepathy, extra limbs. The duergar slaves rise up to challenge their masters.
Orc Examples: Orcs raid the town. The party comes across one of the heirs recruiting young whelps to his cause. The brothers all use scouting parties that ride different steeds: dire wolves, giant spiders, and giant bats.
When the players go anywhere, throw another encounter at them. Every time. Just overload them completely. They should always have the option to complete their mission or to chase a white rabbit. The world should feel alive. Factions don’t stop pursuing their motivations just because the party is on a mission.
This will invariably lead the party to arguing about what they should do. That’s where you buy time to plan which encounter you should throw at them next.
Set up encounters that will be interactions between the factions. This will create tension that drives the campaign. It will also allow the players to loop back on story beats.
Examples: The orcish stronghold sits atop the mines where the duergar collect reagents for the company, leading to territory clashes. The orcs raid a workshop and drink unfinished concoctions that cause horrible mutations (see: Orc Nurtured One of Yurtrus).
When the players interact with different aspects of the campaign, these dynamic factions can react to their success. This allows you the freedom to run your sandbox without worrying about whether the party will zig or zag.
Example: If the party clears out each orcish tribe, the alchemy company will move into the area and the environmental hazards will increase. If the party shuts down the company, the orcs will become more powerful by raiding their remaining laboratories.
The key to running a successful sandbox is putting enough options before the characters to keep them busy. You can control the walls of the sandbox by weaving the scenarios into cohesive elements of the campaign. When they go off script, the factions will be alive enough to keep the sand from going everywhere.
Just make sure to dump out your shoes before you come back inside.