The Castle of Traps is the 18th chapter of Tsubasa: Reservoir Chronicle.
As Syaoran, Fai and Kurogane prepare to invade the Ryanban's castle, Chu'nyan still insists to go with them. Like her mother, she wants to fight them and to bring down their oppressive rule. However, Syaoran holds firm and leaves Chu'nyan to Sakura's care. Fai comments that it is better that they had left Chu'nyan -- he feels that if she had accompanied them to fight the Ryanban, she may end up in trouble once they, the strangers to her land, have left. The three, in any case, agree that they're attacking the Ryanban not only to give him a taste of his own medicine... but, more importantly, to retrieve Sakura's feather if he does have it.
Meanwhile, the Ryanban and his son watch their approach from deep within the castle. The Ryanban detects that Syaoran is carrying a strong power -- nonetheless he doubts that it would be enough to defeat his secret magic.
Kurogane manages to open the castle's gate, however since the castle is protected by the Ryanban's magic, strange phenomena occur (for instance, the sky is on the ground, and vice-versa). Fai suggests that they use Yuuko's magic ball, to which Mokona heartily agrees. It tells Syaoran to throw it as far as he can, until it reaches the castle. Syaoran hesitates for a second, but then hurls the ball toward the castle. As they watch, the magic around the castle disintegrates, giving the heroes access within.
More of the Ryanban's magic awaits them inside, however Kurogane notices that they've been walking down the same corridor forever, with no doors or exits. Syaoran mentions that they have actually been walking in a circle. Apparently, he left a game piece near the entrance when they first walked in.
Fai then walks toward a wall and states that they don't need to walk any further. He feels a lot of strong magic concentrated behind that area, and that could only mean that the Ryanban would be behind that wall. Kurogane says that he thought Fai didn't use magic any longer, to which Fai retorts that what he did wasn't magic, it was just intuition. With his immense strength, Kurogane punches the wall, revealing not the Ryanban, but a mysterious beautiful enemy...