As stated previously, I'm taking some inspiration from what other games do, and peppering in a bit of what I think would make it fun for a game set in Primeval Thule (or other sword and sorcery settings, such as Dark Sun or the kingdoms trodden on by a certain barbarian's sandaled feet).
The important parts to a sandbox adventure seem to be the following, as set out in traditions long before I was around:
- A stretch of territory from which players strike out and explore
- A home base of operations (or at least a small handful of places the players can offload loot, rest, train, and find work)
- Activities to carry out between adventures
- Rewards for exploring aforementioned territory and clearing it of threats
For sandboxes, it's more important to monitor the things players and DMs sometimes gloss over in more story driven or module-based adventures. Encumbrance, daily expenditures of food and water, and any lodging costs the players must pay are critical to track, because a big part of the early game is about being able to afford living to see the next day and keeping your gear in optimal condition. This kind of gameplay doesn't appeal to everybody, so if you found yourself surrounded by players who would grouse constantly about that kind of minutia-tracking, this works just fine without those rules (though some of the challenge is lost).
Games have been doing this forever, but the tack I like to take revolves around the principle of hexploration; that is, a hex mapped overland area that is uncharted (or at least little-known), contains a few settlements, and is chock-full of adventure locations. These locations range from undiscovered villages of isolated peoples to ancient sweeping ruins stalked by the servants of eldritch horrors.
A good-sized hex map for my hypothetical sandbox game for regular adventuring types would be anywhere from 25 to 50 hexes square, using the kingdom-level scale as outlined by the Dungeon Master's Guide, with each hex about six miles across.
My hexes will have the following qualities:
- Level. Each hex has a level from 1 to 20, like a player character. This helps me determine the general difficulty of creatures and lairs present in the hex, as well as how much experience a party receives for "clearing" it (which I will go more into).
- Lairs and Dungeons. A hex can contain monster lairs (like a single small fort or small cavern complex) or dungeons (much bigger and more dangerous). These can be designed by hand or determined randomly; the DMG has great tools and tables for this already.
- Settlements. A hex with a settlement can act as a way station for tired adventurers, as well as trading posts for enterprising merchant-heroes who want to offload unusual loot.
- Natural Resources. This is everything from the mundane to the fantastical; timber, gold, iron, gems, herd animals, ancient menhirs, alien plant growth, and more are all included here.
- Law. A hex is usually lawless, but players who go out of their way to establish some kind of order in a given hex will keep it from repopulating with nasty critters as the seasons pass.
This kind of map puts a lot of work on the DM to establish what the area of play looks like, and what lives in it. If you're very meticulous, you might go out of your way to determine the qualities of every single hex in the area, but it's easy to go overboard. In reality, as anyone from the American Midwest will attest, there are huge stretches of nothing much for miles and miles and miles. There's a happy medium that I could spend a ton of articles talking about, but for sake of expediency, let's assume that only 25% of your hexes contain something interesting, like a settlement or lair/dungeon.
At the simplest level of this sandbox, adventures will take the players out of a safe location into the dangerous wilderness to perform a task for a patron, acquire treasure and fame, and return home to spend the winnings on downtime activities to improve their characters. As they go along, players will "clear" hexes of dangers and exhaust tapped resources at those locations.
Before the campaign starts, the DM should roll 1d4 for each hex to determine its level. This makes some locations much nastier for beginning players without being absolute death traps; though a particularly devious DM might include a small number of hexes that are 1d6, 2d4, or even 1d10.
Clearing a hex awards players experience equal to an encounter of the level of the hex. As such, low-level hexes don't provide much of a challenge to seasoned adventurers, and high-level hexes are naturally more dangerous adventure locations with greater rewards. Players shouldn't know what is in a given hex by number, mind you -- this is all information for the DM to keep on their copy of the map.
There's an inherent danger for players that wander into a given area if they don't know what lives in it. This creates plenty of chance for interplay and information gathering before the adventurers set out to learn from locals or guides what might dwell in a particular area. They might learn that their patron has set them on a quest that takes them through the territory of a flesh-eating chimera, or along a trail where bandits are known to prey. This could make them drive up their negotiated price.
Much of this is old hat to experienced DMs though, so next time I'll present a sample hex map for a location I might use for a sandbox and all of the supporting information for the constituent hexes. Stay tuned!