The clever ape who orchestrates the deception in The Last Battle is Shift.
Shift is the principal antagonist of The Last Battle, the final published Narnia novel. He lives near the Great Waterfall with Puzzle, a donkey whom he manipulates into wearing a lion skin and pretending to be Aslan. Shift then uses the false Aslan to control the talking animals and justify policies that benefit himself and the Calormenes.
His deception grows into a political and religious fraud. Shift claims that Aslan and Tash, the Calormene god, are really the same, a doctrine that helps him secure outside support. The scheme collapses when the real Tash is summoned to Narnia. Shift is ultimately thrown into the stable where Tash is present and is devoured.
Shift is often confused with Puzzle because Puzzle is the animal who physically impersonates Aslan. Ginger the cat and Rishda Tarkaan also help drive the plot, but Shift is the mastermind who begins the deception and turns it into a system of coercion.