Lets take a look at the chars...
Elven wiz11 vampire (often polymorphes to a hill giant),
a dwarven clr11,
a gnome druid5/shifter7 (likes to wild shape),
a human barbarian5/rogue2/ravager5 (STR 22) and a
sor6/dragon disciple5 (STR 30).
It seems that you have alot of magical firepower in that group. The melee capabilities seem to be dependant mostly on shape shifting with the exception of the Barbarian. I can see why your asking about traps though. Your players will use area spells to wipe low hp creatures and can buff up to wipe out tanks. A few well used traps can inflict the bulk of your damage for you.
First, if you dont have it already, get either Traps and Treachery or Traps and Treachery 2. I own the first book, and some of the traps in there are exaclty what you need. (Like the stone acid cylinder that drops on a player, trapping him inside, and then fills with acid (full immersion in acid is 10d6 per round).
Have you done that? Good, now use these suggestions.
Here are some combat suggestions:
Make Pin Cushions:
You have two mage types (the wizard and the Sor / Dragon Diciple). Such characters generally have low AC. Missile weapons are nice in that you can have 20 or 30 Kobolds with Crossbows focus fire on one target.
Also, once someone is identified as a spell caster, have those who are gunning for him ready their actions until he begins to either attack or cast a spell.
Take or Destroy their stuff:
It is quite likely that you will be able to deplete their equipment without having to take it all at once. There are a few ways to do this.
1) The Minotaurs might not have the necessary endurance to go toe to toe with the players in melee, but you might get off a few successful Sunders.
2) When in melee, have 3 or 4 sorcerers use Mage Hand or Telekenisis to remove magic items (identified by way of Detect Magic before hand). When a sorcerer gets some gear, he will then run away with it. Target all such efforts against ONE player. Take the Wands, Rods, Staffs, and weapons first.
3) If you can successuflly disarm someone, have another combatant who used a delayed action to pick up the disarmed weapon.
4) Disintigrage or Shatter items where possible.
5) Environment damage from say, heat, could damage weapons and armor.
No rest:
Many Dm's will often fall into the trap of only running one fight per game day. This means that the players will usually be fully healed and have a full compliment of spells available for every fight. Unless the players take some very reasonable steps to insure otherwise, you can keep them from resting and recovering between fights. Your players can probably handle most big fights easily enough, but try hitting them with that young adult dragon when they have burned about 60% of their spells and are at minimal HP.
If your dungeon lords have the resources, you should assume that someone is always scrying or trying to scry on the players. With that in place, you can even go ahead and pull a dispel on their magic shelters once in a while.
Now, back to the 'tactical' traps.
Trolls Bull Rush:
If you want to get some nasty use out of yoru trolls, have them bull rush weaker casters into deep holes with lots of spikes at the bottom. This works very well if you have a small chasm with spikes at the bottom. A Troll will heal. Go for the Wizard / Sorcerer with this. He probably does not have such a great Str score.
Divide and Conquer:
Put some missile combatants with very good cover at the far end of a corridor. Someone will probably close to melee. Once they pass point X, drop a massive stone plug (or a contingency Wall of Stone) between him and his friends. Also bring out the re-enforcements for your combatants.
Golems And Gas:
Set aside a room with some small Kobold sized Stone Golems / Gargoyles, and have the door made of stone. The door slams shut. Since its a "Golem Door", give it lots of hp and a brutal AC. Fill the room with a Cloud Kill or other toxic gas. Since Golems dont breath, the PC's have an intresting problem.
Dispel Dangers:
Have a room or series of rooms that contain magical spells holding back some very dangerous environment or creature hazards. This will allow you to force the players to think twice about carelessly using dispel magic. No player wants to accidently dispel the walls holding back the Magma.
Illusion Fun:
Once in a while, have the PC's enter a room and set of Contingency Illusion spells. Nothing gets the attention of the players like saying "You enter a large caven, its far side lost in shadows. Two green lights suddenly appear about 20 feet in front of you, the glow giving you the vague outline of a black dragon preparing to inhale. Please roll initiative." After initiative is determined, hand notes to those who made their saves. This trick is nice, since you can often have PC's burn a few magical item charges, potions, and spells uselessly.
Bait:
Use something to lure your players into danger. A large empty room with stone statues is going to make your players suspicious. A large room with stone statues and a young paladin fighting a demon and being terribly out matched is another. Your players will assume you want them to resuce the paladin. They will be suprized when they learn that the paladin is called "Render the Bloody Handed", a demonic sorcerer who then disappears when the statues activate, and uses improved invisibility and some well chosen spells to antagonize the players.
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