I design very complicated chambers and rooms: it’s one of my flaws. For example, a few months ago I had this one room that was a huge natural cave full of stalactites and stalagmites, with a drider living high up on the ceiling, hidden among all the stalactites. He fired barbed arrows at the PCs below as soon as they entered his line of sight, but the PCs couldn’t spot him in the gloom, with all those rocky fissures and spider webs. Only way to retaliate was for the two magic-users to send their familiars – an owl and a crow – and have them fly up close to the drider, in order to see it through the eyes of the birds – and then use that knowledge to help the ranger aim and fire his bow in the right direction. But the closer the familiars got to that elusive drider, the more vulnerable they were themselves (an arrow can be lethal when you only have 4 Hit Points). I even made a little chart for it. One familiar @ medium range = low chances To Hit, need 17. One familiar @ long range = lousy chances To Hit, need natural 20. Two familiars @ close range = good chances To Hit, you only need 14. Etc, etc.
What do you think happened? Players can’t figure out complex shit like that right in the middle of a stressful combat scene. In video games, sure, no problem: game release date is May 2, and on May 4 there is already a teen somewhere in Philadelphia who got to level 19 and figured out that “drider’s cave + familiars” thing and put a 35-minute walkthrough up on the Internet for everyone to see. But that’s video games. It’s different. It’s taken much more seriously, and players are generally alone in a basement, with ample time to think. But a bunch of forty-year-old guys around a table on a Saturday afternoon, with all the excitement and Doritos and beer and coffee and cigarettes? I don’t think so. Not a suitable environment. Waiting for one of the magic-users to say: “Hey, I’ll risk my familiar’s life and send it up the cavern to try and spot that damned archer! Stand by with your own bow, my ranger friend!”
Not going to happen.
I had another room which I called “The Ossuary”, and I didn’t even use it in a game. It was somewhat of an extreme affair. Basically, it’s a regular ossuary, in which thousands of skeletons are packed in tight niches and stacked on wooden shelves – the skulls up front, facing outward, and the bones / ribcages behind, in no particular order. When PCs enter that place, nothing happens. They can explore the entire room, and even get to the treasure cache at the far end. That’s when the monster awakens: twin skeletons, and they instantly attack the intruders. Now, when these two special skeletons withstand any damage (half the damage with edged weapons), they don’t crack or break, but instead, random ribs and femurs shatter here and there on the various shelves of the ossuary. Fact is, ALL THE BONES in there are actual Hit Points (or fractions of Hit Points) for those two “invulnerable” skeletons: the whole Ossuary is just one nasty monster with 180 Hit Points.
The solution is for the fighters to tackle those physical skeletons, while all the other PCs run freely around the ossuary with their clubs and daggers and staves, and smash skulls + bones as quickly as they can. I thought they’d each roll 1d6, every round. On a roll of 1, no bones are smashed that round, and the PC takes 1d8 points of electrical damage: the room’s Ritual tries to “protect” itself. On a roll of 2 through 6, I’d substract that many Hit Points from the Ossuary’s 180 total.
A group of 7 characters have something like 50 Hit Points between themselves (level 2 or 3, let’s say). So, it’s their 50 against the room’s 180...
This picture shows how I playtested it all – twice! First playtest: I had the players find the “trick” on round 2, and at the end of the scene, the cleric was down, the Dwarf only had 1 Hit Point left, but the group survived. Second playtest: I only had the players find the trick on round 6, and the PCs all died in the end. Having “the idea” is definitely key here; figuring out that any character can start shattering bones in the niches and alcoves really makes the difference between Everyone Dies and Everyone Lives...
Too risky for my own taste. Seven player characters die because no one had the right inspiration at the appropriate moment? That’s crazy.
If you work at Blizzard, Rockstar, or whatever, do that: create complicated puzzles, have fun with space, distances, time windows, lines of sight, and all that. But if you’re a good old DM in a good old tabletop RPG, calm down: just design a room with a pile of gold at the far end, and monsters standing in the way; want the gold? fight the monsters! Puzzles are unwelcome in tabletop RPGs, except maybe in Cthulhu because that vibe is different and atmospheric. But in D&D, anything past a basic riddle is a total waste of time, slowing the game to a stall. Riven was very cool, but it was certainly no RPG. My word of advice is simple: keep it simple.