Hiiragizawa, Eriol

柊沢エリオル

Eriol Hiiragizawa serves as the primary antagonist in the latter half of the series, a segment often referred to as the Master of the Clow arc. As the reincarnation of Clow Reed, Eriol possesses both Clow's memories and his entire magical power. He wields a magical staff resembling Clow Reed's, commands Clow's creations Yue and Cerberus, and has fashioned his own pair of similar guardians: Ruby Moon and Spinel Sun. He relocates from England to transfer to Tomoeda Elementary School after Sakura Kinomoto passes the Last Judgement and becomes the official master of the cards. At school, he appears as a quiet, mature boy, although he also displays a mischievous side by regularly joining classmate Takashi Yamazaki in fabricating complex lies about the history of objects, places, and events. While he seems like a normal student to Sakura, Syaoran Li is suspicious of him. It is soon revealed that Yue and Cerberus can detect his magical signature as Clow's, forcing Eriol to erase Yue's memories after Yue accidentally sees him.
Eriol came to Japan to aid Sakura and compel her to use her own magical powers to convert the Clow Cards into Sakura Cards. This conversion is necessary because the cards draw their magical energy from their master; until Sakura converted them, they could not use her magic and were slowly dying. The guardian Yue was also suffering the same fate, which forced Sakura's brother to "feed" him all of his magical power to prevent Yue, and his false form Yukito, from dying.
Sakura remains unaware that Eriol is causing the magical disasters that force her to convert the cards until near the end of the series, when Eriol reveals himself to her. He puts the city to sleep and challenges Sakura to convert the last two cards, the Dark and the Light, which must be converted together. After Sakura successfully does so, he tells her that she is now more powerful than Clow Reed and asks her to perform one final task: to divide his own magical power between himself and her father Fujitaka—the other reincarnation of Clow Reed—so that Eriol will no longer be the most powerful magician in the world. He then takes Sakura, Syaoran, Tomoyo, Yue, and Cerberus to his home, where he explains why he had to give her a reason to convert the cards, as doing so without a need could have sent the cards out of control or drained Sakura's own life.
Eriol's true age is unknown, as he used his magic to halt his aging process to remain the same physical age as Sakura. He is romantically involved with Kaho Mizuki, whom he originally sent from England to aid Sakura in the Final Judgment and who offers Sakura support through letters during the second arc. At the end of the manga series, she returns with him to England, and in the second anime movie, they are shown together when Sakura calls for advice.
In the anime series, Eriol is the sole reincarnation of Clow Reed, with all elements from the manga regarding Fujitaka's relation to Clow and the inheritance of half of his powers removed. The final explanation at Eriol's house is also shifted slightly so it takes place the day after the final battle, rather than immediately after, and it occurs because Sakura seeks him out rather than him giving an invitation.