Yue was mentioned constantly in the second half of the Clow Card arc when Sakura began to have dreams of the Final Judgment though at first it was Kaho Mizuki who appeared in the dream rather than Yue himself. When Sakura first described her dreams to Kero and mentioned someone with cat eyes he remained silent and as Sakura was leaving he warned her that someone was now watching her and she should be careful.
The closer Sakura came to the Final Judgment the more powerful Yue's presence became, especially during the full moon. Though Yukito was still unaware of his true nature Yue's aura would occasionally bleed through during the full moon, having a bizarre effect on those around him. When Sakura and Yukito were on a scavenger hunt, Yukito pointed out the early rising full moon. The aura bled through and caused Sakura to pass out from being so close to a stronger magic force but it assumed that she was just tired at the time. Kero once sensed Yue's presence after the Dark cards attack but Mizuki's presence caused him to mistake her for Yue's false form.
The Light and Dark cards eventually alluded to Yue's presence by subtly hinting to Sakura that "He's been right beside you all along.", much to Sakura's confusion.
Yue makes his first appearance when Sakura captures the final Clow Card, The Earthy. He then announces that he must judge Sakura's worth: If she can defeat him in combat, she can be the Mistress of the Cards. Sakura, however outright refuses to harm him, in part because Yukito Tsukishiro, a young man for whom Sakura cares deeply, is his temporary form and would be likewise wounded.
Also, as she confirms in the manga chapter entitled "The Final Judgment" because of her natural determination to befriend even the most distant of people she encounters. At first, Yue was determined that nobody succeed Clow Reed, and even threatens to shoot Sakura when she tries to ask him about it.
Eventually, after transforming her staff to one of her own star power with some help from Clow Reed's Moon Bell, Sakura manages to subdue Yue without harming him by capturing him in a ball of wind created by the Windy card. She then asks Yue about Clow, and follows up with a speech in which she tells him that she would rather be his friend than his master.
About me: Personality: On the outside, he acts cold, aloof, and is much more serious and intimidating than his counterpart Cerberus. However, he was revealed to still have a kind heart. He shared a special bond with Clow Reed that made it hard for him to accept Sakura Kinomoto as a "replacement" for his creator during the Final Judgment. However, Sakura manages to work her way into his heart as a dear friend
Powers and Abilities: Yue's powers are based on the Moon and come from Eastern magic. Unlike Cerberus, Yue's powers are heavily dependent on the power of his master. However, after receiving Touya's powers, Yue became able to sustain himself.
Moon Shields & Barriers: Being a perfecter of the Clow Cards, Yue and Cerberus, both, can create strong magical shields and barriers, only breakable by either Sakura or Clow Reed.
Crystal Projection: Forming pure white energy in his hand, Yue can create sharp crystal shards that multiply and fly at the enemy with incredible speed. This is likely due to his command over Cards related to the element of Water: the Freeze, the Snow, the Wave, the Bubble, the Mist and the Rain cards.
Moonlight Control and Manipulation: Yue can also create streams of moonlight energy to use as a weapon, which he can form into other shapes, like a bow that can fire arrows made of moonlight.
Magical Perception: Yue has the ability to sense the Clow Cards and magical presences. Upon consuming Touya's magic powers, Yue was able to perceive Clow's presence in Eriol.
Magical Empowerment: By drawing strength from other magical beings Yue can sustain himself and his powers.
Clow Cards: Yue demonstrates the ability to either circumvent or manipulate the power of any Clow cards that fall under his jurisdiction. For example, he cannot be frozen using the Time card, or bound using the Wood card as both are under his jurisdiction. However, once Sakura transforms her star staff, he is unable to control the cards.
Cards
Half of the deck is under his protection, and these are the only cards that can effectively be used against Cerberus, however no candidate would ever have to fight Cerberus. The Elements Yue controls are The Watery (his aggressive element) and The Windy (the gentler Element under his jurisdiction, and the only real gentle Element).
