Vale of Dunan
In series 1, Riddle Bridge was credited as Vale of Dunan, and was always played by the warrior in first place and another warrior of their choosing. The leader would walk the path whilst the other would work the book.
When opened, the book would speak a riddle in rhyme to the warriors, who would then attempt to work it out. Stones were laid out with letters on and so the warrior must spell out the correct answer. If the leader stepped on the correct stones, they would progress to the rings; if they stepped on a wrong stone, they would disappear in a flash of blue fire and lose a life. The helper's life was not at risk. The blue fire is what Raven calls the "Mists of Dunan", the thing that makes the Vale so deadly in such a beautiful area.
At the far end of the stone letters was a skull totem pole with two gold rings on it. Once the warrior reached the rings the curse had been lifted and so they could walk back along any stones on the path. Once they were back it was up to the leader to decide how the rings were given out (whether they would keep both or give one or both to their helper).
This challenge was always played as the last challenge before Way of The Warrior on Tuesday, the last challenge before Way of The Warrior on Wednesday and the second challenge of the day (after Spider Tunnel) on Thursday of each heat. If the leader got the riddle wrong on Tuesday (which they most often did), it'd carry over to Wednesday (Raven would not reveal the answer if the warrior failed). If they got the riddle right on Tuesday and/or Wednesday, a new riddle would be brought out for the next day. If the riddle wasn't correctly solved on Thursday, Raven would reveal the answer.
Vale of Dunan/Riddle of the Portal hybrid
For the final challenge on Day 5 of the third heat, a new challenge (taking place at the Vale of Dunan) was used to determine who'd go into the next level of the tournament. The warrior with the most number of lives would go first. They'd take their place at the foot of the path, whilst Raven would stand at the book. When he opened it, the book would speak a riddle to the warrior, who would have to solve it alone, without Raven's help.
Once they got the right answer, they would walk across the correct letters on the path. They would then have to solve the portal's word puzzle to progress through. They would examine the text carved above the portal, work out the correct thing to say and speak it into the listening rock. When they got it right, the portal would open, prompting the warrior to walk through and into the final of the tournament.
In series 2, Vale of Dunan was redesigned as Riddle Bridge, and the map symbol was changed from a horizontal view of the letters to a vertical view of the letters (now arranged in rows and columns), with a river running underneath and the riddle book off to the left. The name of the challenge was moved from under the side to above the top of the path.
The format was also changed slightly. On Raven's call forth, the warriors in first and second place would stand at the bridge and at the book, respectively. Raven would produce an hourglass from somewhere inside his cape and show the warriors that that was how much time they had to complete the game (normally followed by him urging the warriors to work faster). If they didn't start on the path by the time the sands ran out, or stepped on an incorrect tile, both would lose a life. If this happened, Raven would call forth the warriors in third and fourth place to replace first and second, respectively. The hourglass would be reset. If they lost, and if it was Monday or Tuesday of a heat or final, the warriors in fifth and sixth place would mount the bridge and book, respectively.
At the end of the bridge were either two, four or six gold rings (either loose (two rings), in twos (four rings) or in threes (six rings)). If the first/third/fifth warrior successfully crossed the path successfully and took half the gold for himself, the second/fourth/sixth warrior would follow in his path and take the rest of the gold. Any remaining warriors would follow in their path. (Raven would, presumably, fly over the bridge.)
If all the warriors got the riddle wrong, Raven would resurrect them and take a life from them - normally with a droll remark - and turn to the book for the answer. It would say "The answer is..." and the correct path on the bridge would be illuminated.
In series 8, with the move to Aviemore, Riddle Bridge was re-christened Riddle Path and given a new map symbol.
In series 11, the task is renamed Riddle Rocks. The task is the same - however, the riddle now appears on a blackboard and the two warriors may read it together, rather than being split between reader and bridge-crosser. Only one warrior needs to cross; the other can simply walk around the rocks to the rings after the riddle is answered correctly.
Additionally, the challenge is now given to all the warriors, rather than being given to the first and second-placed contestants and only offered to the others if the leading warriors fail. The riddle is different for each pair attempting to cross the bridge, meaning later pairs no longer have the advantage of having had more time to think about the riddle, as was the case with Riddle Bridge.
In the DVD game of the show, Riddle Bridge is played by the viewer at home. The rules are the same, except asking for the riddle again (by moving the cursor to the book) would automatically reset the timer.