One of the new characters seen in the promotional materials was Cardinal, and the official Twitter account for the series fully revealed Cardinal's designs for the anime.
【キャラクター情報公開！】December 23, 2018
Cardinal's role in the series is a bit complicated to explain without going into major spoilers for the Alicization arc, but suffice to say that she ends up becoming a major ally to Kirito and Eugeo after a few major events take place. Though fans of the series may recognize "Cardinal" as the main operating system of the MMOs in the Sword Art Online universe, and thus there's a significance to her name. But that will all be revealed in due time.
The staff behind the series are just as excited for Cardinal to make an appearance in the anime as fans are as one of the character designers, Suzuki Gou, shared a slick illustration of the character to Twitter shortly after it was revealed that she will be making an appearance in the anime's next big arc. The new arc of the series is set to officially begin with the second cour of the anime, which begins on January 12, 2019 with the series' 14th episode.
SAOアリシゼーション12話御視聴ありがとうございました。次回の放送は来年になってしまいますがお話も盛り上がっていきますので引き続き御視聴何卒よろしくお願い致します✨ pic.twitter.com/q7eTF8zUyI— 鈴木 豪🐾 (@kurogomasama) December 22, 2018
If you have yet to catch the new season of the series yourself, Sword Art Online: Alicization can currently be found streaming on Crunchyroll, Funimation, and Hulu. The series is officially described as such:
"Where... am I...?” Before he knows it, Kirito has made a full-dive into an epic, fantasy-like virtual world. With only a murky recollection of what happened right before he logged in, he starts to wander around, searching for clues. He comes upon an enormous, pitch dark tree (the Gigas Cedar), where he encounters a boy. “My name is Eugeo. Nice to meet you, Kirito.” Although he is supposedly a resident of the virtual world - an NPC - the boy shows the same array of emotions as any human being.
As Kirito bonds with Eugeo, he continues to search for a way to log out of this world. Meanwhile, he remembers a certain memory deep down within him. He remembers racing through the mountains with Eugeo as a child... A memory that he should not have in the first place... And in this memory, he sees someone other than Eugeo, a young blond girl. Her name is Alice. And it is a name that must never be forgotten...”