Conjuration: There are nine ledges around the perimeter of the room, one every foot or so starting ten feet off the floor, each one lined with porcelain monsters.
Clue: Magic is only as real as you make it. (Or something better.)
Problem: Each porcelain monster has an identical porcelain key for the locked door. The players have to climb up to the ledges and break a porcelain monster to get its porcelain key, but even if they get a porcelain key without breaking it, the key is too fragile to open the lock.
Solution: The porcelain monsters on the first ledge are all the monsters from the summon monster i spell, the porcelain monsters on the second ledge are all the monsters from summon monster ii, and so on. Casting any level of the spell makes the porcelain version of the summoned monster disappear, and the summoned monster appears with an iron key that will open the door. If the characters try to summon a monster whose porcelain version was broken, the monster appears but it is dead (possibly carrying a twisted or broken key). Characters can try to summon monsters from spell levels higher than they can cast, but it doesn’t work because they can’t cast those spells yet.
The DM should decide whether the iron key vanishes with the summoned monster when it is dismissed, when the spell ends, or if the summoned monster is killed.
Instead of one font, many fonts. Some with standard keys and some without any keys, and one with the invisible glass key. Some of the standard keys have magic auras (but not divination magic).Divination: The room has a marble font filled with water.
Clue: Though the choices are many, magic often shows us the way.
Problem: The door leading out of this room has a hundred keyholes and the key is nowhere to be found.
Solution: Detect Magic: The glass key, which has the same refraction index as the water in the font, glows with divination magic and the locks glow with a variety of schools, but only one keyhole glows with divination magic as well.
Or, instead of fonts, a shallow pool. The bottom is covered with images of keys. Most of the images have a real key on top of them. Two keys in the pool have a divination magic signature — one is the invisible glass key, and the other is actually the image on the bottom of the pool beneath a bronze key. The keyhole in the door doesn’t open the door. The real keyhole is hidden in the bow (round part you hold) of the image with the divination magic signature, on the bottom of the pool.
Any objects in the room are illusory. Features and textures on the walls are also illusory, so the door and keyhole are illusions as well.Illusion: One wall of this room is a mirror.
Clue: Lies and facades are tools: use them rather than be used by them.
Problem: No key is found in this room, but the reflection of the PCs have demonic features on them: glowing eyes, stunted limbs, a puss-filled eye, etc. Additionally, the reflection shows each of the PCs carrying a key on a leather thong around their neck.
Solution: Disguise Self too look like the reflection causes the key to appear on their necks.
Once the characters match their reflections (have their reflections change to normal if they drop disguise self and you are feeling merciful) the characters can pass through the mirror wall. Their reflections either disappear, enter the illusory room as illusions and continue to mirror their characters’ movements, or enter the illusory room (changing back into demons if necessary) and attack anyone left in the room. (But the demon reflections cannot get back through the mirror wall.)
The real door is in the real room on the other side of the mirror wall.
Instead of falling apart all at once, make cuts melt or reshape the blade in obvious but minor ways. They only get the key by fully committing — once someone has actually been stabbed, the blade comes out of the character’s body as the key. Maybe throw in a WILL save to stab themselves, if appropriate.Necromancy: Floating in the center of this room is a sharp looking knife.
Clue: The knife that does not draw our blood, bends to our will.
Problem: No key is found in the room.
Solution: False Life or any magical temporary hit points, that allows the person to cut themselves with the blade without causing injury to their primary hit points, causes the blade to fall apart, revealing the key within.
Throw in some water dripping up from the floor to the ceiling pool so they have a chance to figure out the reverse gravity before they get caught in it.Transmutation: High on the ceiling of the room is a large round hole, which is filled with water, that seems to defy gravity. “Floating” on the surface of the water are delicate glass orbs. One has a stopper and an iron key is within, but the other orbs are filled with blue-white crystals. Deeper in the water, at the top of the water-filled chamber is a small keyhole.
Clue: Changes in your environment, might require a change in you.
Problem: A reverse gravity directly under the hole will cause anyone moving there to shoot up to the water, shattering the crystal-filled orbs, causing them to explode, freezing the water and damaging the PCs.
Solution: There are several potential solutions, but the simplest would be casting Feather Falling and falling into the water slowly enough as to not shatter the globes, allowing the PC to grab the key and “sink” up to the keyhole.