Lyman Banner, known as Daitokuji (大徳寺?) in the original Japanese language version, is a fictional character in the Yu-Gi-Oh! GX anime series. He is a teacher with a very funny accent, has a fat, cute cat named Pharaoh , and is therefore addressed as "Daitokuji-sensei" (大徳寺先生?) in the Japanese version. In the English version, Banner is voiced by Wayne Grayson, while Kappei Yamaguchi takes the role in the Japanese version.
A fabled alchemist and member of the Shadow Riders, Banner largely supports the protagonists for most of the first season of the series, though he is directly responsible for numerous events meant to orchestrate the revival of the Sacred Beasts.
Banner's character design was overseen by Kenichi Hara. His usual outfit consists of a white shirt, black pants, belt and necktie. His black hair is tied back in a ponytail. Throughout the entire series, Banner's red eyes are constantly hidden behind their lids and a pair of square-lensed glasses, except during the second half of his Duel with Jaden.
As Amnael, Banner wears a hooded tunic with a flowing red scarf, boots, and a mask with yellow eye-pieces. On his right hand is a glove made of heavier material, and he carries a black model of the Academy-issued Duel Disk on his left despite the second Japanese opening sequence featuring him with the standard Disk given to all students and staff before his official debut as Amnael. In this incarnation, he has white hair, and the sides of his face are covered in pronounced veins and cracks.
The concept illustrations for Banner's facial expressions were identical for both his regular and costumed appearances.
In the timeline of the Yu-Gi-Oh! GX anime, Banner was working on his alchemic research long before his arrival at Duel Academy, intent on creating the legendary Philosopher's Stone. His studies led him to discover an ancient tomb during the same period of time when Maximillion Pegasus first discovered Duel Monsters. Within, he unearthed three stone tablets adorned with the likenesses of the Sacred Beasts. In the English version, he was cursed for this intrusion, while in the Japanese version, he would later be stricken with a fatal illness. To prolong his life, Banner developed a homunculus in his own image to transfer his soul into his new body. However, it began to crumble, so he resolved to joining the Shadow Riders as its seventh and final member in order to attain the power of the Sacred Beasts to fulfill his dreams of creating the Philosopher's Stone, and use it to obtain immortality.
Banner was eventually hired as an alchemy professor of the Slifer Red dormitory at Duel Academy. While there, he lured several Obelisk Blue students including Atticus Rhodes into the abandoned Obelisk Blue dormitory, where they disappeared. He would resume his job without coming under suspicion, ultimately charged with watching over Jaden Yuki, Syrus Truesdale, Chumley Huffington, as well as the rest of the students of Slifer Red.
Using the pseudonym of Amnael (アムナエル Amunaeru?), Banner systematically defeats Alexis Rhodes and Chazz Princeton when the Shadow Riders put their plans into motion, taking their Spirit Keys to open the gate behind which the Sacred Beasts are sealed. He locks Alexis, Chazz, and Atticus within the Emerald Tablet,which holds his Shadow Charm on the cover, and guides Jaden to his lair with his sigil to challenge him to a Duel. Upon his defeat, Banner gives Jaden his Emerald Tablet, and with it, the card, Sabatiel - The Philosopher's Stone. His original mummified body and homunculus vessel then dissolve into dust. From then on, his soul resides within the body of his pet cat, Pharaoh, though he would return on occasion in subsequent seasons to assist Jaden.
Banner's personality varies greatly from his original Japanese counterpart in terms of his actions and intentions during the Duel with Jaden. In the English version, Banner lies about having rigged all of Jaden's Duels so that he would be chosen as one of the Key Keepers, and confesses that he joined the Shadow Riders to prepare him for the final battle against Kagemaru. In the Japanese version, Daitokuji never does this, and instead views Judai as a "fusion genius" who must face adversity head on in order to learn the secrets of alchemy which have allowed him to triumph. He is last seen with Jaden running off to another adventure.
In the original series counterpart Daitokuji ends the majority of his sentences with "nya" (Japanese cat onomatopoeia).
Banner plays an Alchemy deck, which draws a relationship between the science and universe. His strategy relies on the removal of his own cards from the game through Chaos Distil and Macro Cosmos, supported by the Special Summoning of Alchemy Beasts (錬金獣 Renkinjū?), based on common base metals and animals used in alchemy to transmute and refine gold, and the Alchemic Processes, based on four of the seven main stages in transmutation. References are made throughout his deck to concepts in alchemy, including mentions of the Ouroboros, the Seal of Solomon, Hermes Trismegistus, and the macrocosm and microcosm philosophy.