The Maze Card has the ability to make a maze in a different dimension. It is invisible on the outside, but whenever a person enters the area The Maze is affecting, they are trapped within it. The Maze keeps the people inside from 'cheating', such as by flying over the walls, by drastically increasing the height of the walls. Though Kaho Mizuki's Moon Bell seems to be capable of destroying Maze's walls without them repairing themselves. The main body of The Maze is that of a labyrinth with green walls. It is under The Earthy Card.
The Maze first appears in Episode 26. Sakura, Syaoran and Tomoyo enter the Tsukimine Shrine and are suddenly trapped inside Maze. At first, Tomoyo suggested putting a hand to the wall. Sakura then asked Syaoran about using his Lasin Board to find a way out, but it fails, as it was created to only find Clow Cards and they were currently in The Maze. Then, Sakura used The Fly, trying to see The Maze's layout, but the higher she flew, the higher the walls became. Finally, Ms. Mizuki came with her Moon Bell and beat down the walls in a straight line to an exit. Because Ms. Mizuki was the one who primarily helped the trio get free, The Maze chose her as its master, but she gives it to Sakura.
The Maze is transformed into a Sakura card in Episode 66. She transformed Maze in conjuncture with The Illusion to create a walkthrough planitarium effect to distract people while she tried to find the source of Clow Reed's presence.
CCS Manga- Volume 3: pages 171-174
CCS Manga- Volume 4: pages 1-9, 25-34