Reynard - I can see this is also a very strong playstyle issue as well. I don't do sandbox games like that. My games, whether as a player or a DM, almost always feature fairly strong plots, meaning that randomly wandering over to places on the map just doesn't happen in the games I play.
I think that's a reasonable position to take when actually designing adventures, but when designing a setting/sandbox, it doesn't hold. I mean, big powerful things are likely to be well known (feared), at least enough to give a clue they are there, but if the 3rd level PCs head into the Swamps of Doom where the hag covey lives (and likes to dine on travellers) they are responsible for their demise, not the DM.
I never put a Maguffin in a place where monsters of higher power reside. If the group learns they need to recover the Ancient Spear of Malamorte, its going to be a place of CR-suited monsters.
They have a fair warning as to general monsters in the area: northern mountains have giants, the underdark has mind flayers and drow, and everyone has heard the rumors of the undead inhabiting the gloomfen swamp.
No "gotcha" monsters. This is what I meant by "surprisingly high CR monster among a bunch of low-level foes" that Older D&D modules loved to occasionally do.
Zoning Rules. Here is where things get a little meta-gamey. Most of your common, low-land areas have minor nuisance foes (goblins, orcs, etc) that are challenges early, but not later on. Similarly, local crypts rarely hold undead more powerful than ghouls or shadows, etc. You have to go to remote areas for powerful monsters to appear (hill giants don't live near hamlets, elder dragons don't build dens near inhabited city-states, and liches want more privacy than the local cemetery). When higher-level adventures happen, its because the adventurers went to the remote locales where they live or the monsters came down to visit the civilized lands (such as a githyanki incursion).
Try to pace rumors and adventure hooks to match the appropriate level. No Rings of Ultimate Power at level one quests.
When all else fails, give the PCs a bit of meta-info. It never hurts to occasionally explain that Hill Giants are CR X, or that The Lich Arthgard is known to have cast 8th level magic.I'd have to say preference for mostly. I don't honestly have that much experience with sandbox games. Even way back in 1e and B/E D&D, we ran a lot of modules. The idea that you just plop the party in the middle of somewhere with nothing really going on and no particularly reason for them to be there and not somewhere else isn't a way I've ever really played.
There was always some reason for what we were doing. It might be thin, hackneyed, cliche and 99% crap, but there was a reason.![]()
No "gotcha" monsters. This is what I meant by "surprisingly high CR monster among a bunch of low-level foes" that Older D&D modules loved to occasionally do.
Zoning Rules. Here is where things get a little meta-gamey. Most of your common, low-land areas have minor nuisance foes (goblins, orcs, etc) that are challenges early, but not later on. Similarly, local crypts rarely hold undead more powerful than ghouls or shadows, etc. You have to go to remote areas for powerful monsters to appear (hill giants don't live near hamlets, elder dragons don't build dens near inhabited city-states, and liches want more privacy than the local cemetery). When higher-level adventures happen, its because the adventurers went to the remote locales where they live or the monsters came down to visit the civilized lands (such as a githyanki incursion).
While I'm about to embark on the Savage Tide AP, I think the best campaign would combine both sandbox and themed. An adventure matrix I believe it's called where you have four or five fairly distinct adventures ready to go at any given time/level. The players choose which ones they want to do, and can move from one to another and then back again as they want and is reasonable to do.
I have done sandbox adventures - like the original Isle of Dread - lots of times. But, I've never done an entire campaign that way.