Idea: A crumbling and ancient castle, built untold eons ago by giants in the frigid north, now inhabited by yetis and undead giants.
Hook: A ruin of giant make has been found, and a map on a stone tablet recovered from the ruin gives the location of an ancient giant stronghold, along with promises of treasure.
1. A vast mural on the wall, depicting giants fighting against dragons and other, less nameable beasts. One being in particular, a vast, skeletal thing with gnashing teeth, has a massive slash carved into the stone where it is depicted. (Those skilled in theology or the occult may be able to recognize some of these beings as demon gods of hushed folklore. The one with the slash is a demon god of hunger and cannibalism.)
2. A huge, petrified wooden desk is up against the wall. (On top of the desk is a huge cracked stone tablet covered in giant runes. If translated, it explains that an unearthly affliction has cursed the fortress, and begs for reinforcements. It cuts off abruptly, and is stained with blood.)
3. An enormous pile of bones stretches up near to the massive ceiling, the bones all being incredibly ancient and large, belonging to giants. Nearby crouches a huge naked humanoid thing, covered in white hair. (This thing is an undead giant who committed grave acts of cannibalism of his own kind before he died, and returned as a famished monstrosity. He is hibernating, but if the characters make enough noise or get too close, he will awaken and attack.)
4. A huge throne, covered in carvings of giants constructing massive fortresses and slaying monsters. There is a huge skeleton atop the throne, wearing a huge crown made from the tusks of elephants, and holding a rusted dagger in its hand. There is the glint of gold in its teeth. (The glint comes from one massive gold tooth, easily worth 1000 coins. There is a hole in the skull, evidently self inflicted.)
5. This room is vast and held up by pillars, but appears completely empty, yet somehow enormous banging sounds seem to be coming closer, and there is a fetid odor in the air. (There is an invisible undead giant, only detectable by the sound of its massive footsteps and the stench of death. It is invisible due to a ring on its finger, which can be worn as a crown by anyone who might manage to slay the beast.)
6. The floor is extremely cracked in places, and some holes have already formed. (Characters must tread carefully through this room, otherwise they may fall through the floor and fall into a great pit beneath the fortress, full of stalagmites.)
7. A group of 7 yetis, thin and hungry. They will attack upon being able to smell the intruders. In the corner of the room is an enormous chest, evidently used for storage by the giants. (Contained within the chest is mostly broken rubbish, but there is a large chain of gold, evidently once used as a necklace, worth 2000 coins if returned to civilization. The yetis are easily distracted by food, and may even be able to be made docile if fed.)
8. There is a vast machine here, with a giant sized lever. There is an open metal door to this machine, and a closed metal door. (If something goes into the metal door and someone pulls the lever, the door will close. After 1d6 minutes and a lot of grinding noises, the closed metal door will open briefly, and out will come the original object, now made of solid steel. This will, unfortunately, kill any living things that go through. After this, the input door will open and the machine is reset.)
9. The room here does not appear as crumbling and deserted as the rest of the building, and a small tent can be seen in the corner. (Tripwires are all over this room, rigged to crossbows tipped with a deadly venom. In the tent lives a lonely hermit named Grigori, bearded and taciturn. He is the last of a party that once led an expedition here. His most prized possession is a massive red gemstone, worth 1000 coins, that was once the earring of a giant prince. Grigori has an antidote for the venom.)
10. The great vaulted ceiling is held up by a statue of a giant. There are engraved giant runes on the pedestal of the statue. On the ceiling are murals of horrific monsters. (These runes read; All praise Thalduin the mighty, he who holds up the heavens to keep the Things from beyond at bay.)