What is Mokona?
Mokona is the white, rabbit-like creature assigned to guide the Magic Knights through Cephiro: round as a manjū bun, with a red gem set in its forehead from which it produces whatever the journey needs, tents, food, and supplies. It does not speak. Its whole vocabulary is one sound: “Puu.” For most of two series, that is all it is allowed to be.
Then, near the end of CLAMP’s manga, Mokona explains itself. It is the creator of Cephiro, of Earth, and of the other planets, and the author of the laws of each, including the Pillar system; it created Cephiro’s order after watching what the people of its earlier creation, Earth, did with theirs. It summoned the Knights the second time itself. The mascot was the god of the world all along, riding in the party’s arms.