Oh, that is exactly the sort of thing I'm looking for. Any specific ideas?
Not sure if this is too much detail for this thread, but:
In an adventure I ran recently at a local game day (slightly modified from the first adventure in my Eberron campaign), the PCs entered an old dungeon to discover a Large statue of a dust devil (which they had fought eariler in the adventure) in the center of a room. The twelve squares around the dust devil all had carvings on them: the three in the NW quadrant of the room were carved with arcane sigils, the three in the NE quadrant of the room had of holy symbols, the three in the SE quadrant had carvings of weapons and armor and the three in the SW quadrant had pictures of plants and animals. The statue itself radiates magic.
To be frank, the purpose of the carvings was just to get all (or most of) the PCs in the room instead of having them send only one guy in to check out the statue while the rest stayed safely outside.
![Devious :] :]](http://www.enworld.org/forum/images/smilies/devious.png)
In both the games I ran, all the Arcane PCs gathered in the NW quadrant, the Divine PCs in the NE quadrant, the Martial PCs in the SE quadrant and the Primal PCs in the SW quadrant.
Physical or magical interaction with the statue (touching it, or better yet,
deliberately trying to invoke its power) causes two things to happen:
1. A secret passage opens.
2. A strong gust of wind erupts from the statue, attacking everyone in the room: +10 vs. Fortitude (so it's not
entirely a railroad; I have a
small chance of rolling low, after all.

). Those hit are pushed through the secret passage into another room and stunned for one round. Once this happens, the wall of the other room starts to move. After one round, it will close off the secret passage. During this round, those still in (or just outside) the statue room have a choice: run in after the other PCs or stay where they are. If they stay where they are, the secret passage is blocked off by the moving wall after one round and they miss out on the next encounter (again, no railroading!

).
The PCs who end up in the room beyond the secret passage face the following non-standard trap-like skill challenge:
In addition to the crushing wall, the PCs should also notice that sand starts filling the room and a howling wind roars through the room making concentration difficult (-2 penalty to all checks). There is a door on the opposite wall of the room, but what appears to be a spiked ball of force is directly in front of the door. Ask the PCs to roll initiative. The room acts on initiative count 10.
The room is 8 squares by 8 squares at the start of the encounter. On initiative count 10, the wall advances one square (pushing adjacent PCs one square when it does so). Each round, a PC can prevent the wall from moving for one round by making a DC 16 Strength check. The PCs can stop the wall completely by finding the mechanism with a DC 16 Perception check and disabling it with a DC 16 Thievery check.
The sand gradually makes movement through the room more difficult. In the first round, after initiative count 10, the PCs have to make a DC 12 Acrobatics check each round or treat the floor as difficult terrain. On the second round, the DC increases to 16 and in the third round it increases to 20. After initiative count 10 on the fourth round, the floor is difficult terrain and the PC have to make a DC 12 Acrobatics check each round or spend an extra square of movement to move into each square. The DC increases to 16 on the fifth round and 20 on the sixth round. After initiative count 10 on the seventh round, the PCs must make a DC 12 Athletics check to move one square. From the eight round on, the DC increases to 16.
A PC looking for the source of the sand realizes that a nature spirit is bringing the sand into the room with a DC 16 Nature check. The PCs can get the spirit to stop with two successful DC 16 Nature checks, or scare it off with two successful DC 16 Intimidate checks (or one of each).
A PC who examines or tries to stop the wind realizes it is created by divine magic with a DC 16 Religion check. The PCs can get the wind to quiet down (removing the penalty to all checks) with two DC 16 Religion checks or two DC 16 Diplomacy checks (or one of each).
On initiative count 10 each round, the ball of force makes a melee or ranged attack against the PC closest to the door: +5 vs. Reflex; 1d10+4 force damage. A PC who examines the ball realizes it is created by arcane magic with a DC 16 Arcana check. The PCs can dispel the ball with two DC 16 Arcana checks.
The door is locked by four locks. The Lock of the Arcane is covered with arcane sigils. It can be broken if it takes 10 points of damage (it has AC 12, other defenses 10), but it has resist 10 to all damage except damage from arcane spells. A character who examines the lock and succeeds on a DC 16 Arcana check can unlock it with another DC 16 Arcana check. Similarly, the Lock of the Divine is covered with carvings of holy symbols, has resist 10 to all damage except damage from divine prayers, and can be unlocked with two DC 16 Religion checks; the Lock of Nature has carvings of plants and animals, has resist 10 to all damage except damage from primal evocations, and can be unlocked with two DC 16 Nature checks; the Lock of Craft has carvings of weapons and armor, has resist 10 to all damage except damage from martial exploits, and can be unlocked with two DC 16 Thievery checks.