He purifies Lex, every 4 turns.
He is a dark-light blue cat, with dark blue stripes on his head, and swirly dark-blue patterns on his fur, has a curly tail, always smiling widely. He goes invisible for a bit (As seen in "Treasure Room.). He also speaks formally.
His first, true appearance, is on the dialogue, when Mother Goose, and Lex, goes into the Forgotten Forest. (Book 4, Chapter 6) He warns Lex about the warp tiles. When Lex was confused of the directions, Cheshire Cat, told him to go through the rabbit hole. He also warned about the Caterpillar, which may "delay" his journey with Mother Goose, with his smoke and illusions. When the Caterpillar was defeated, Cheshire Cat appears in a mushroom, going visible. Which now, makes him, Lex's second companion.
1. He is based on himself, in Lew Carroll's Alice's Adventures in Wonderland.
2. His color, refers to the color of the Purify Potion. This may be, why Cheshire Cat's has the ability to purify Lex.