Once of the more unique characters Mario will come across during his journey is one being referred to as the Desert Wanderer. Mario can find the Desert Wanderer originally in Sand Kingdom, but then he will hop from kingdom to kingdom as Mario continues to find him. Each time you can find the Desert Wanderer, he will award you with a free Power Moon and give you a hint as to where you can find him next.
Since you must complete certain tasks during the story before finding him, it is recommended to search for him after completing the Main Story. You can find him in the following Kingdoms (in this specific order) to obtain up to seven Power Moons: Sand Kingdom, Metro Kingdom, Cascade Kingdom, Luncheon Kingdom, Moon Kingdom, Mushroom Kingdom, and Sand Kingdom (once again).