This post might feel weird for some, because it has always been one of the DM's tasks to provide maps for the group. And for good reason: maps have always been one of the key elements of an encounter, adventure and campaign, especially when combat is involved. And maps have always been the guide for both players and DMs alike to know who or what is where.
[ Before I continue, let me point this out: I am not referring to just board-based maps, I'm including in the discussion mentally-pictured maps, in the so-called "gridless games". Even if you don't draw a map, the fact that, even if it's just in the mind of the DM, you've pictured how many prison cells are in the section of a prison, and where the guard station is relative to the prison cells, and where in the guard station the guns, rations, and other supplies, and where the PCs are relative to everything else, that's still everything mapped out in your mind. ]
This post isn't going to tackle map-making tricks like pre-drawing maps, having players have their own maps that they'll track, "fog of war", and other techniques that other DMs have done and posted. No, this isn't "I'll have one player draw my map for me", either. This post is going to do something completely different: have the players do the map-drawing. Not other DMs, the *players*.
Heretical? Lazy DMing? Maybe, but hear me out first: Last week, I was in a bit of a pinch. I had quite the mental roadblock in our weekly Eberron campaign, as I was able to make my monsters, and I had a generic idea of what my encounters would look like, but I didn't know how to make those combat encounter maps more engaging and interesting. So, I told the players, "alright, I'm going to let you guys use your imagination on this, this is the situation, what do you see?"
The resulting map was very hilarious, as one player said that because they were on a snowy mountaintop, "it's snowing". Hence, the entire map involved slightly obscured and difficult terrain, among other unexpected outcomes.
Apparently, this approach isn't really THAT new; in http://story-games.com/forums/comments.php?DiscussionID=2982 [UPDATE: Error in accessing link, might no longer be available] jhosmer1 describes him allowing his players to contribute minor details on the map, that might be useful during their stay there. The difference is, instead of allowing players to just add dressing to the map that could potentially be useful, I've allowed my players to shape the map according to how they imagine it.
Also, part of the inspiration for this idea could be attributed to the Vignettes style of playing in the Dungeon Master's Guide 2, where players are assigned characters who they eventually role-play in ways they want, so instead of telling the story yourself, they tell the story in their manner. In this case however, instead of telling the players what their characters see, the players tell the DM what their characters see.
Now, the first obvious problem with this is that players could abuse this right by placing in things that they know they could use to their advantage.
1. You're only putting on the board what they see and know about.
2. There's a good chance that most of the map that they see, the enemy either sees it, or knows about it.
Now if a player rolls a high enough Perception or Thievery check, I could allow them to put something that the monsters in the map don't know about (but you as the DM know), or find something that normally they wouldn't know about (like a trap or two), but otherwise it's basically as above.
Update [this is based on the crucial bit that was commented in that blog]: Actually, let them. The question is: if the players -- whose characters are level 1 for example -- put a +5 Vorpal Longsword in the middle of a seemingly nondescript room, why is it there? What happened to its previous wielder that caused such a powerful blade to just lie there untouched? Having the story develop around this concept should help further enhance the fun of that session and campaign, because you give your players greater empowerment and the ability to express themselves in ways outside their character(s)... although as was taught to Spiderman: with great power, comes great responsibility. So it's not exactly my fault as a DM if the players explained that the Vorpal Sword was lying there because its previous owner was overwhelmed by the swarms of creepy crawly bloodsuckers... that are now heading towards the party... is it?
The second problem is that the DM does not have complete control over the map. However, what some might view as a problem, I view as an opportunity: because the players are more engaged in the designing process, it's also a chance to be surprised at what could be possible during an encounter, and allow you to do some pretty interesting twists to the story.
I'm still exploring the whole "player-drawn encounter maps" concept as it stands, so I'm still going to see what are the advantages, disadvantages, and fixes, but so far here's how I've been doing it:
1. Prepare your materials. Expect some heavy refluffing and on-the-fly tweaking on your monsters and traps, if ever the players do something completely unexpected.
Update: Only do this if you're into preparing stuff. For those who can afford to just make stuff up on the fly (e.g. using 13th Age's Relationship Dice, a chart or two and a bit of houseruling here and there), feel free to ignore #1 and head straight to #2.
2. Give a general description of the map and scenario. For instance, telling the players that they are inside a dungeon, a forest, or some other area. It's very likely that this would jumpstart the group's creativity.
3. Have players each contribute at least one feature of the map, whenever possible. Alternatively, have the players interested in exploring the map contribute primarily to the map-building.
If ever the group lacks ideas on how the map should look like, that's when you fall back to drawing the map's features yourself.