I wrote this as a reply to Mike Mearls’ blog, but it’s worth standing on its own.
I learnt the art of improvisation when I ran my Amber Diceless RPG campaign back about 15 years ago. You pretty much had to do it. Of course, when improvisation failed, there were some pretty awful sessions. 🙂
Making situations interesting is great. The more players have to react to, the better. Six goblins in a 20’x30′ room isn’t interesting. Six goblins in a cave with many branching and connecting (wide) tunnels is fascinating. It’s the difference between “Keep on the Borderlands” and “Fane of the Drow” – while Keep is a superior adventure, I think Fane gives much better encounters. Watching the goblins run away and hurl javelins on the Mithral Mines map, thus separating the party who were chasing after them, and then have Duergar attack from an unexpected entrance… that was really great.
I don’t think the Fantastic Locations line really worked – the maps were too specific, and the “adventures” too bare – but I think they did get DMs (and designers) thinking about how to get the game more interesting, rather than just the new type of monster.
So, throw a second group of enemies at the party, or make the terrain do something unexpected (a fissure appears), or a wave of fog (poisonous?) boil out of the earth!
There’s a big difference between presenting a challenge to the group and redefining the rules. The PCs are created with a certain contract – the rules of the game. If you redefine those, you’re making invalid all of their decisions. Presenting a challenge to them just means they get a chance to use their abilities, although you have to be careful about giving too much of the same sort of challenge – if you can’t sneak attack anything (see Age of Worms/Dawn of a New Age), or if magic works against nothing, or you can’t get to your opponent (Savage Tide/There is No Honor) then things get boring and frustrating very quickly.
One of my favorite games was due to me using the random dungeon generator in the old AD&D DMG; my players were exploring a nearby ruin, and I hadn’t prepared it all in advance. At one point, they came to a “trick”. Hmm. I quickly made up this enjeweled throne, which the PCs, one by one, sat on. The first was rewarded by a fall of 10,000 gp worth of gems. Wow! The second changed gender. Hmm. The third… was contacted by the ruler of the dungeon, an imprisoned Knight of Hell. That improvised trick changed the course of the campaign.
I use a lot of pregenerated adventures simply because I run so much D&D (three campaigns at present). One problem I have is that I stick too much to the text of the adventure and don’t improvise so much; when I do – as I did for the Necropolis campaign – things get a lot more interesting…