Théo, known as Prince Cloud in the original Japanese version, is a prince who joins Princess Silver on her quest. He has blond hair and blue eyes, and is typically attired in white tights, a blue tunic, and a crown.

Initially appearing as an antagonist when he petrifies the king and queen, this act is later shown to be a protective measure to save them from the Grim Reaper. His true aim is to help defeat the Grim Reaper and break the curse.

He is characterized by competence and arrogance, often speaking with blunt honesty about Silver's many flaws, which regularly causes friction between them. Despite this, he shows steadfast loyalty and frequently steps in to protect Silver and her companions from harm. A skilled swordsman, he is generally capable in most situations. One of his few weaknesses is a strong aversion to green peppers, though he eventually learns to overcome it.

A complex relationship exists between him and Silver, blending bickering with mutual attraction. Their interactions are filled with constant arguments yet also moments of mutual concern. Silver develops a crush on him, and there are signs he may return these feelings. Their dynamic plays a key role in Silver's personal growth, as his criticisms push her to face her own shortcomings.

His background includes a forgotten first meeting with Silver during their childhood. He was once known as Prince Klin before taking his current name. On the journey, he assists in gathering the seven pieces of the Grim Reaper's apology letter, which are essential to finding a way to defeat him.

After the Grim Reaper is defeated and the king and queen restored, he occasionally returns to aid Silver in further adventures, such as a quest to recapture two mischievous accidentally freed angels. He eventually becomes a member of the group traveling around the kingdom.