Okay, I've fallen behind so time to make up some big-time time. (lol, Fogg quote

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First, something about the highly controversial War Fan episode. Along with my previous observations, I'm really thinking the Dark Forest is not a possibility, because it needs to be possible to encounter all three temple guards, so if it was in the Dark Forest, either the Dark Forest or the Room of the Secret Password had to be a dead-end. However, other than that first episode in Season 3, they didn't have any completely dead-ends in the third season. You could argue that it could be a situation similar to The Thornwood Gavel of Judge Roy Bean where they put one guard on each path and both paths lead to the same place, but I'm really doubting that here since we're talking about two rooms that were both adjacent to the artifact room.
The War Fan episode may be on the table for a long time, but this is my position on it.
Now, onto the episodes you've all covered:
THE BENT SHAVING PAN OF JEDEDIAH SMITH:
The door to the Chamber did not open, so I'm thinking it was in the Ledges or the Quicksand Bog. I'm more thinking the ledges, because I believe I can see a silhouette of a temple guard in there at some point.
THE MARBLE ARMREST OF XERXES:
Based on the path they took and what doors unlocked, it seems that all three encounters were forced, unless they put the other guard in the King's Storeroom. I doubt that though, because they kind of made it obvious where the half-pendant was, which hints that all three were forced. Though, it was almost impossible for the frontrunner to miss, but easy for the second runner to forget. So, I'm saying Password, Shrine, or Warriors.
THE SMASHED PRINTING PLATE OF FREDERICK DOUGLASS:
Could have been in the Crypt or the King's Storeroom. To me, either seems equally likely.
THE MYSTICAL SPELL BOOK OF THE IMPERIAL WIZARD:
The only place that makes sense is the Chamber of the Sacred Markers.
THE MYSTERIOUS MANUSCRIPT OF MARY SHELLEY:
Because of how dark it was in the Ledges (seriously, it was REALLY dark in there this time), I'm thinking the guard was in the Ledges. However, something strange happens in this episode and I have a theory why. While the first runner is in the Room of the Ancient Warriors, the middle suit spins around as if a temple guard were in there BEFORE she tried that suit. I really think a temple guard was supposed to be in there, but because of the screw-up, he was unable to grab her. This, combined with the abnormally long time it took the guard in the Shrine to come out makes me think that since the guard screwed up in the Warriors, they told him to just go to the next room to make the capture. THIS IS JUST A THEORY EXPLAINING A STRANGE HAPPENING.
THE DRIED APPLE-HALF OF WILLIAM TELL:
They didn't make it far enough to know where the other guard was, but I have a theory. Since they had two pendants and the first two guards were unavoidable, it seems pointless to make the third encounter optional, so I'm thinking it was in the Dark Forest or the Shrine of the Silver Monkey, because they already went through enough rooms that the upward passage from the Dark Forest to the Shrine should have opened.
THE IVORY HUNTING HORN OF ROLAND:
Definitely, one was in the Quicksand Bog, because in the credits, they do a first-person view down the Shrine-Bog passage and we clearly see the pile-up of blocks hiding a temple guard. I'm going to say the other was either in the King's Storeroom or the Chamber of the Sacred Markers, based on which Pit doors opened and where the half-pendant was.
THE LOST HORNPIPE OF THE PIRATE CAPTAIN:
Definitely in the Ledges.
THE ENORMOUS FEATHER OF THE ME LINH:
I'm saying the Ledges because of the darkness again, plus the only other option is the Room of the Secret Password, which really seems unlikely considering their path.
THE BROKEN TRIDENT OF POSEIDON:
It is difficult for me to piece this one together. I can only assume there was an alternate path up the central column and through the Room of the Ancient Warriors. However, if this path is true, a temple guard in the Chamber of the Sacred Markers would be behind the cover, but when she grabs the Trident (and before she DROPS it), that cover slides up, showing the absence of a temple guard there, ruling out the Chamber. So, what's left is the Ledges, the King's Storeroom, and the Room of the Ancient Warriors.
THE LILY-CRESTED CROWN OF CLOVIS THE FIRST:
Youtube's crappin' out on me for this episode, so I can only go by nicklegends' temple diagram. Could be in the Ledges, Password, or Dark Forest.
On a final note:
We are getting close to the end, but I would like to keep this topic active so people will continue to discuss it until we can figure out definite answers. After we get to the last ones, I will go through a comprehensive list of what episodes we still need answers for and what possibilities we narrowed it down to.