When the players are talking, take a book and slam it on the table loudly (but don't let them see you do it). Then start the encounter.
Double check that you aren't playing on a glass tabletop. Or maybe that'd make it all the better.
One thing I did in my last campaign, I started them off in the Howling Horde but changed the Moradin temple to one of Tharizdun. At the beginning of the quest, they found that the entrance to the cave was laced with a black material they were able to identify as foreign to the area. I stressed the covering of the Shaman's room looked like it had been stitched together from an old, purple robe.
The sanctuary was the last thing they explored -- after killing the dragon, the goblins, the hobgoblins. They stopped at the door before a break and everyone went to smoke but me (I had to usher one of the other players out) and quickly formulated a plan. When they came back in, I was standing by the light switch and had turned off the lights in the rooms surrounding and spoke in a slow and quiet and authoritative voice. I'm typing this from memory, so some details are probably wrong.
"Do you go in?"
"Yes."
"As you remove the bar and slowly swing the heavy wood doors open, a wave of cold washes over you and then nothing." *lights off*
"What happened?"
"It's too dark to see."
"I'm a dwarf, do I see anything?"
"It's too dark to see."
"Uh-oh. What about the microwave (speaking of the Warforged Pally)? Can he see?"
"Barely. It's still too dark for Ward to make anything out."
"Well...let's light torches?"
"Alright."
"The torches glow brightly and then dim, almost to embers but you can make out what's in front of you for a few feet. Elves, dwarf and warforged can see almost six feet in front of you. As you collect your senses, it is deathly cold and you hear the slow drip of water. Drip. Drip. Drip. Drip." I continued the drips until the party found what caused it, stopping only answer questions or provide exposition.
"Let's make search checks." *rolls* I inform them that they can take a twenty if its a trained skill with ranks.
"You find that the room is about forty by forty feet. It seems carved from black stone, not constructed. Several rows of pews line the floor but have rotted from age. As you walk, dust plumes into the air. At the farside, it tapers into small, raised alcove with a pedestal that seems to raise up from the black stone. At each corner there is a statue that has been smashed. Along side the wall with the door, a cistern lies smashed and the slow drip of water comes from there."
"Uh-oh. Well, let's loot. Keep a look out for monsters, shadows and ghosts." *rolls*
"The next thing you notice about the room is, starting from the center of the floor, there is a spiral engraved. When it meets the walls, it seems to circle upwards to the ceiling, slowly, before becoming a proper spiral and ending in the center of the circle." *I began drawing a spiral on the map with a marker and didn't stop until one of the players noticed and mentioned it was kinda creepy.*
"That's not good. Is there anything else?"
"Each statue seems to be made out of a different colored stone, one red, blue, green, purple. *The warforged states he grabs a piece of each individual state* Inside the blue one is a iron triangular prism that seems to be made out of silver. It is about six inches in length."
"I grab it."
*smirk* "When you grab it, your soul feels chilled and you take *roll* 3 points of cold damage."
"At least I have cold resistance."
"No, you don't understand. You take 3 points of cold damage."
"Microwave, you want to give it a shot?"
"Alright, I grab it."
I mull this over quickly, but my warforged character has said he specifically wanted no soul and that was his quest. "You touch and hesitate for a second, but nothing happens as you lift it out of the rubble. You can tell it is cold, possibility the coldest thing you've ever touched."
"Odd. Is there any frost or anything on it?"
"No."
"I dip it in the cistern."
"As you push it in and pull it out, *a small "That's what she said" aside* the water beads aimlessly off of it."
"No frost?"
"Nope."
"Odd. Is there anything else?"
"The pedestal, when searched, has a small triangular hole in its base."
"I bet this thing is a key. Let's try it."
"When you place the prism inside the hole, you hear a small click."
"We turn it. Does anything open?"
"A compartment, previously unnoticed even by dwarf eyes, pops open. Inside is a scroll, a robe, a pendant and a knife."
"What does the scroll say?"
*I read the same text included with Howling Horde with the necessary adjustments*
"Creepy. What does the robe and pendant look like?"
"The robe is deep, lustrous purple. It has a high cowl and a hood. If you could imagine a gay KKK member." *laughs* Sometimes easing up on tension creates a more profound impact when you deliver your next punch. "The pendant is that of Pelor's but black. Blacker even than the stone you stand on."
Warforged: "Obviously, this is a thing of evil. I make a knowledge religion check." *rolls*
"You've heard of a symbol like this, but nothing substantial in your studies. But you are sure of your assumption of evil."
*there is a small debate of what to do before a player makes a decision*
The tiefling (of course): "Well, I put on the robe."
"You don't feel the cold anymore. In fact, you're rather comfortable."
"Awesome. I cast detect magic."
"There is nothing magic in this room, other than some of your group's possessions."
"But the robe?"
"Mundane."
"I put the pendant on, too."
"It feels heavy, probably more than it should be."
"Alright...I grab the dagger, too."
"You feel alright. Make a will save for me."
"..." *roll* Honestly, I didn't care about the result. Rolls, especially when the cause isn't given, add tension.
While, he was rolling, I pulled out my phone, something I usually don't do. Between that and the fact it was still dark, my players took notice and my girlfriend gave me a scowl for breaking my own rule. I sent my tiefling player a text, something along the lines of "As you grab the dagger, you notice an inversed ziggarut blaze at the base of the blade and then fade. A single word rocks your mind, 'Tharizdun.' But otherwise you are fine." However, he rolled pretty low on his will save so I had an idea pop into my mind afterwards. He asked if it was okay if he read the text aloud, I said it was his to share.
"Tharzidun."
Warforged: "Huh? I make another check." *rolls high for K(R)*
"You've heard this name whispered but only in the brightest of locations and only between elderly Pelorites. It is a name of outstanding evil and destruction."
"Dude, you need to take that stuff off and give it to me."
"Alright. I take off the pendant and the-"
"When you remove the pendant and Ward takes it from you, you feel hollow. As if everything you've ever desired is that pendant. You need it back."
"...Microwave, maybe I should hold on to it."
"No."
"Why not? I'm fine. I just need my precious...I mean..."
"Yeah, you're not getting it back now."
"I'll gut you of your wires and parts!"
At this point I had officially driven a wedge between the characters. One person took up for the tiefling, saying that the group could deal with it later. the others restrained the two and threatened to knock out the Tiefling and tie up the Warforged.
There was other small talk and debate that night. But the drama hung heavy for the rest of the campaign. The players made sure the other one was actually upset. They found a priest of Pelor who said he did not feel comfortable handling the symbol but directed them to someone he knew who could. The campaign ended before we got to that point, or anything else involving Tharzidun. Sadly.
