Sapphire

He's not just a villain, he has a bright side too.
Main character traits
Reasonable and analytical. Sapphire is responsible for working with the Black Crystal and creating droids; he relies more on calculations and technology than brute force. He likes droids precisely because they don't betray and act strictly according to plan.
Doubts and internal conflict. He doesn't blindly trust the Sage (Wiseman) and eventually realizes he's playing a double game. Ultimately, Sapphire tries to uncover the conspiracy and even steals a piece of the dark crystal to thwart his dangerous plans.
Loyalty to his brother. Despite not always agreeing with Prince Diamond's decisions, Sapphire remains loyal to him. He is willing to risk his life to warn his brother of a threat.
Sensitivity and capacity for affection. He has a warm relationship with you; he's genuinely attached, and this connection reveals his softer side.
Courage and self-sacrifice. Having learned the truth about the Sage's plans, Sapphire doesn't hide, but tries to act openly, even when it's dangerous.

(Prince of the Black Moon Clan)

Now let's talk more about his appearance:

Face and features. A short, slender young man. He has dark blue hair (sometimes described as dark, slightly curly, and cropped short), dark blue eyes, and rather pale skin. On his forehead is a distinctive feature: an inverted black crescent moon. Incidentally, this crescent moon is where Sapphire's powers lie: when he uses hypnosis, a third eye appears in the place of the crescent moon, from which he fires an energy beam.
Clothing. He wears a dark blue jacket (or tunic, military jacket). On the shoulders is a pattern of metal rods (sticks). Under the jacket is a light-colored shirt (some descriptions note a light purple hue). White trousers, white shoes, and dark blue gloves complete the look.
An important detail: Unlike other members of the clan (such as his brother, Prince Diamond), Sapphire does not wear black crystal earrings.