Go to Part 1
SPOILER WARNING!
The following thoughts contain minor spoilers for Keep on the Shadowfell. If you don’t want to be spoiled, don’t read it. And if you’re in my gaming group then you definitely shouldn’t be reading it.
THE CHERUB STATUES
When I remixed the first part of the Chamber of Statues, I didn’t think I’d be discussing the second part of that encounter. Why? Because there was nothing seriously wrong with that section of the encounter.
… or so I thought.
I’ve been cross-posting these mini-essays on Keep of the Shadowfell to WotC’s forums, and the discussion there revealed there was actually a rather serious problem with that section of the encounter.
In this section of the encounter, there are four cherub statues. When triggered, the cherubs create an arcane cage to trap a victim. The cherubs then pour water into the arcane cage, which triggers a whirlpool effect that smashes the victim into the cherub statues and cause them to take damage.
The key element to this encounter is the arcane cage that the statues create:
ARCANE CAGE (immediate interrupt, when a creature walks past the northern two statues; encounter)
The statues create a wall of arcane magic to enclose the area between the four statues. The wall lasts as long as at least three statues remain intact. The wall cannot be damaged and is affected only through the destruction or disabling of the cherub statues.
The key problem here is the phrase “create a wall of arcane magic to enclose the area between the four statues”. When I first read that phrase, I interpreted it as meaning that the arcane cage enclosed the entire 4×6 hallway, including the cherub statues. But then I realized that the other half of the encounter talks about the dragon statues reacting to characters outside the arcane cage attacking the cherub statues, so I concluded that the arcane cage must only enclose the 2×4 area between the cherubs.
I thought the phrasing was a little unclear, but no big deal.
Except it turned out I wasn’t the only one who had interpreted that phrase differently. In no time at all, in fact, the conversation included four mutually incompatible interpretations of what the arcane cage did and they were all legitimate interpretations of the phrase “create a wall of arcane magic to enclose the area between the four statues”:

To this muddle we can also add some confusion from the phrase “when a creature walks past the northern two statues”. There seem to be two meaningful possibilities for this:

(Of course, if you go with the second possibility for the arcane cage, the answer to this question is pretty obvious — it’ll be the one that actually traps the triggering character inside the cage.)
PROBLEMS, PROBLEMS, PROBLEMS
In trying to work out how this encounter is supposed to work, we can try to narrow the possibilities down by taking two facts into consideration:
(1) Barrier effects “run along the edge of a specified number of squares”. Since each statue is entirely within one square, the statues either have to be inside the barrier or they have to be outside the barrier — they can’t be both.
(2) The dragon statues are supposed to be able to use their force shot ability against characters outside the barrier making attacks against the statues. Therefore, the statues have to be outside the barrier. (And even if this wasn’t true, you wouldn’t want a scenario where the only character who can lower the cage is the character trapped inside the cage: If they get killed by the whirlpool effect, not only are the irretrievable, but the location of the cage effectively prevents the rest of the group from reaching the end of the adventure.)
Thus we can conclude that it must be one of these two scenarios:

… except these doesn’t actually work.
First, because the cherubs have to be inside the cage (they’re pouring water into the cage and the trapped character is slammed against them for damage).
Second, because under this interpretation the guy inside the cage is effectively taken out of the game: There’s nothing they can do to escape. All they can do is hang tight, soak up the damage each round, and hope somebody gets them out. (This second problem isn’t necessarily unworkable, it’s just a questionable design choice.)
In short, the encounter doesn’t work. The cherubs have to both inside and outside the cage and, according to the rules of the game, that can’t happen.
As I see it, there are two options:
(1) Use the 2×4 option and then break the rules, basically creating an ad hoc ruling that the character inside the force cage can attack and destroy the cherubs even though they shouldn’t be able to.
(2) Redesign the encounter so that each cherub statue takes up 2 squares (and, thus, you can have them half-in and half-out of the arcane cage without breaking the rules).
FUEL ON THE FIRE
After writing up this whole analysis, I was looking through my friend’s copy of the Player’s Handbook and discovered something that only serves to deepen the confusion over what the arcane cage is supposed to be doing.
In the Quick Start Rules that came with Keep on the Shadowfell, there were three areas of effect defined: Barriers, Blasts, and Bursts. In the PHB, on the other hand, barriers no longer exist. They’ve been replaced by walls.
Here are the rules from Keep on the Shadowfell:
Barrier: A barrier runs along the edge of a specified number of squares. A barrier must cross at least one edge of the origin square.
And here are the rules from the PHB:
Wall: A wall fills a specified number of contiguous squares within range, starting from an origin square. Each square of the wall must share a side—not just a corner—with at least one other square of the wall, but a square can share no more than two sides with other squares in the wall (this limitation does not apply when stacking squares on top of each other). You can shape the wall however you like within those limitations. A solid wall, such as a wall of ice, cannot be created in occupied squares.
I have two reactions to this:
(1) Why wasn’t this fixed in the Quick Start Rules? Yet another example of sloppy editing.
(2) The encounter still doesn’t work.

It can’t be option #1 because the arcane cage is a solid wall (otherwise you could walk through it and the trap would be pointless), and therefore it can’t be formed in the squares occupied by the cherub statues.
It can’t be option #2 because walls must fill contiguous squares and each square must share a side — not just a corner — with at least one other square of the wall.
It can’t be option #3, obviously, because then there’s no interior of the cage for someone to be trapped in.
It can’t be option #4 because the trigger for the arcane cage would either result in no one being trapped inside or would make it impossible for the wall to form (since the triggering character would be occupying one of the squares the wall has to fill).
There are two possible ways of handling this:
(1) You can use option #4, change the trigger for the trap (so that it goes off when a character enters one of the squares inside the arcane cage), and then ignore the rules so that the cherubs are somehow inside the cage (despite the fact that they’re nowhere near the inside of the cage).
(2) You can use option #2 and rewrite the effect so that it creates multiple walls. Unfortunately, it’s not clear whether or not a character inside the arcane cage can attack the cherubs. (There’s a clear rule that says you can’t move across a diagonal if one of the squares bordering the diagonal has a solid barrier in it, but I can’t find any rule that tells you whether or not you can attack through a diagonal where two solid barriers meet.)
THIS IS RIDICULOUS
Needless to say, I consider this to be ridiculous. I consider the complete inability for this encounter to work as written just further evidence that Keep on the Shadowfell was never playtested. Such a shoddily designed encounter would, frankly, be inexcusable in any professional product. But it completely baffles me that WotC evidently spent so little effort and care on the product they chose to serve as the flagship for 4th Edition.