Here is the set of riddle rooms I added to the adventure when I ran it:
4. Riddle Room
The narrow northern passageway continues for another 45 feet, and opens into a small cavern, fifteen feet long by fifteen feet wide. Next to the northern wall, painted onto the hardened earth, is a circle encompassing numerous runic symbols. The circle softly shines with a faint red glow. There are no exists from the cavern other than the one you entered through.
The circle is a magic teleportation device, and a detect magic spell will reveal a strong Transmutation aura.
Any character that steps on to the circle is teleported without error to one of the eight riddle rooms, all of which place the character to the north of the room, with a door to the south (though the players do not know which direction they are now facing without a successful sense direction check). Roll randomly (D6, or if more than 6 players, D8) for each character stepping on the circle to determine which room they teleport to.
Riddle Room 1 –
A flash of bright light engulfs you, and you feel a bit disoriented as the room spins. Suddenly a small room appears before you, five feet wide by ten feet long, made from cold, smooth, white marble. You are standing on a magic circle that looks identical to the one you just left, though it no longer glows. Across the room opposite you is a heavy wooden door. Neatly carved in the door are the following words “I have a mouth but cannot speak, lay on a bed but never sleep.” There are no other exits from the room.
The door is locked (1.5 in thick; Hardness 5; hp 15; Break (DC 18); Open Lock 25). It will magically open if the riddle’s solution, RIVER, is spoken aloud on either side of the door. Characters can hear each other through the door with a listen check (DC 15). Failure results in muffled sounds (recheck allowed every round).
Riddle Room 2 –
A flash of bright light engulfs you, and you feel a bit disoriented as the room spins. Suddenly a small room appears before you, five feet wide by ten feet long, made from cold, smooth, white marble. You are standing on a magic circle that looks identical to the one you just left, though it no longer glows. Across the room opposite you is a heavy wooden door. Neatly carved in the door are the following words “A goblin walked twenty miles into the woods to find me, stopped to look for me when he got me, then threw me away when he found me.” There are no other exits from the room.
The door is locked (1.5 in thick; Hardness 5; hp 15; Break (DC 18); Open Lock 25). It will magically open if the riddle’s solution, SPLINTER, is spoken aloud on either side of the door. Characters can hear each other through the door with a listen check (DC 15). Failure results in muffled sounds (recheck allowed every round).
Riddle Room 3 –
A flash of bright light engulfs you, and you feel a bit disoriented as the room spins. Suddenly a small room appears before you, five feet wide by ten feet long, made from cold, smooth, white marble. You are standing on a magic circle that looks identical to the one you just left, though it no longer glows. Across the room opposite you is a heavy wooden door. Neatly carved in the door are the following words “At night they come without being fetched. By day they are lost without being stolen.” There are no other exits from the room.
The door is locked (1.5 in thick; Hardness 5; hp 15; Break (DC 18); Open Lock 25). It will magically open if the riddle’s solution, STARS, is spoken aloud on either side of the door. Characters can hear each other through the door with a listen check (DC 15). Failure results in muffled sounds (recheck allowed every round).
Riddle Room 4 –
A flash of bright light engulfs you, and you feel a bit disoriented as the room spins. Suddenly a small room appears before you, five feet wide by ten feet long, made from cold, smooth, white marble. You are standing on a magic circle that looks identical to the one you just left, though it no longer glows. Across the room opposite you is a heavy wooden door. Neatly carved in the door are the following words “I never was, am always to be. No one ever saw me, nor ever will. And yet I am the confidence of all, to live and breathe on this terrestrial ball.” There are no other exits from the room.
The door is locked (1.5 in thick; Hardness 5; hp 15; Break (DC 18); Open Lock 25). It will magically open if the riddle’s solution, TOMORROW, is spoken aloud on either side of the door. Characters can hear each other through the door with a listen check (DC 15). Failure results in muffled sounds (recheck allowed every round).
Riddle Room 5 –
A flash of bright light engulfs you, and you feel a bit disoriented as the room spins. Suddenly a small room appears before you, ten feet wide by ten feet long, made from cold, smooth, white marble. You are standing on a magic circle that looks identical to the one you just left, though it no longer glows. Across the room opposite you is a heavy wooden door. Neatly carved in the door are the following words “Eight weigh the same, one does not. Balance them thrice, to find the special slot.” To the right of the door on the wall is a small balance resting on a marble shelf extending from the wall. In a small wooden cup in front of the balance are 9 pearly blue marbles. There are no other exits from the room.
The door is locked (1.5 in thick; Hardness 5; hp 15; Break (DC 18); Open Lock 25). Characters can hear each other through the door with a listen check (DC 15). Failure results in muffled sounds (recheck allowed every round).
The marbles and balance are not magical, however the room radiates a faint illusion glow if Detect Magic spell is cast. No normal or magical method, other than the scale, will be able to detect which marble weighs more or less than the others.
The solution: First balance one third of the marbles on each side of the balance. Roll 1D6 to determine which sets are weighed first: 1-4, one set weighs more than the other; 5-6 the sets weigh the same. Next take one of the group and balance it with one the outside group. That way you know not only which of the 2 groups have the different marble, but also weather that marble is heavier or lighter than the other ones. There are only 3 marbles to weigh, which reveals the answer.
Once the third balance use occurs, the door reveals a small marble-shaped enclosure below the lock. If the player puts the wrong marble in the door, the door makes an audible click, locking with a second lock (same stats as above lock), and nothing further happens. If the correct marble is put in the door, it opens.
Riddle Room 6 –
A flash of bright light engulfs you, and you feel a bit disoriented as the room spins. Suddenly a small room appears before you, ten feet wide by ten feet long, made from cold, smooth, white marble. You are standing on a magic circle that looks identical to the one you just left, though it no longer glows. Across the room opposite you is a heavy wooden door. Neatly carved in the door are the following words “To open, pour exactly 4 Gobs in the hole all at once, no more, no less.” In front of the door on the ground is a small hole that appears to drop forever. To the right of the door on the wall are two stone jars on a marble shelf extending from the wall, one has “3 Gobs” on the side, and the other has “5 Gobs”. To the left of the door is a small fountain pouring up and back down to itself upon on similar marble shelf extending from the wall. There are no other exits from the room.
The door is locked (1.5 in thick; Hardness 5; hp 15; Break (DC 18); Open Lock 25). Characters can hear each other through the door with a listen check (DC 15). Failure results in muffled sounds (recheck allowed every round). Neither the jars are nor the fountain is magical, however the room radiates a faint illusion glow if Detect Magic spell is cast. No player has heard of a Gob of measurement, nor does Bardic knowledge help.
The solution: The player should fill up the 3 Gob jar, and pour it into the 5 Gob jar. Next fill up the 3 Gob jar again and pour it in the 5 Gob jar until that one is full. There is one Gob left. Next empty the five Gob jar in the fountain (or elsewhere, just not the hole) and put the 1 Gob in the five Gob jar, followed by filling the 3 Gob jar again and pouring that into the 5 Gob jar, total 4 Gobs in the 5 Gob jar.
If the player pours exactly 4 gobs is poured into the hole all at once, with at least a two second pause afterwards, then the door opens. If less than 4 Gobs is poured in the hole with more than 1 second between additional water being poured in, or if more than 4 Gobs is poured in the hole, then the door makes an audible click, and a second lock (identical to the first) closes in the door, and nothing further happens.
Riddle Room 7 [BACKUP ROOM]
A flash of bright light engulfs you, and you feel a bit disoriented as the room spins. Suddenly a small room appears before you, five feet wide by ten feet long, made from cold, smooth, white marble. You are standing on a magic circle that looks identical to the one you just left, though it no longer glows. Across the room opposite you is a heavy wooden door. Neatly carved in the door are the following words “The beginning of eternity. The end of time and space. The beginning of every end. And the end of every place.” There are no other exits from the room.
The door is locked (1.5 in thick; Hardness 5; hp 15; Break (DC 18); Open Lock 25). It will magically open if the riddle’s solution, THE LETTER E (or just “E”) is spoken aloud on either side of the door. Characters can hear each other through the door with a listen check (DC 15). Failure results in muffled sounds (recheck allowed every round).
Riddle Room 8 [BACKUP ROOM]
A flash of bright light engulfs you, and you feel a bit disoriented as the room spins. Suddenly a small room appears before you, five feet wide by ten feet long, made from cold, smooth, white marble. You are standing on a magic circle that looks identical to the one you just left, though it no longer glows. Across the room opposite you is a heavy wooden door. Neatly carved in the door are the following words “I’ve more heads than any hydra and more tales than the longest book.” There are no other exits from the room.
The door is locked (1.5 in thick; Hardness 5; hp 15; Break (DC 18); Open Lock 25). It will magically open if the riddle’s solution, SACK OF COINS, is spoken aloud on either side of the door. Characters can hear each other through the door with a listen check (DC 15). Failure results in muffled sounds (recheck allowed every round).
There is a marble hallway five feet wide and fifty feet long, connecting each of the Riddle Room doors. Once one player makes it through their door, they can attempt to assist another player who is stuck, either by trying to pick a lock, break a door, damage a door until opened, or yelling to help solve their riddle. In the center of the hallway is an archway over a 10 foot wide cavernous, wood-lined passageway leading to the south. The air smells a bit metallic in this direction.