Mr. Phoenix

Mr. Phoenix was the father of Aster Phoenix and a card designer for Industrial Illusions. In the Yu-Gi-Oh! GX anime, he created the "Destiny Heroes", while in the manga he created the "Legendary Planets". In both cases he was killed (kidnapped in the English dub) and his creations were used for malicious purposes by the antagonist of the respective version.

Anime
Mr. Phoenix worked as a card designer for Industrial Illusions. He eventually began creating the "Destiny Heroes". Seeing this as an opportunity, The Light of Destruction influenced Phoenix into creating a vessel to house it's essence. Though he tried to resist, he was unable to, and eventually created "Destiny Hero - Plasma". This card was infused with the Light of Destruction, who then began to seek a human host. By chance, Phoenix's son Aster let a design concept blow away in the wind, and in chasing after it bumped into The D, a criminal who was down on his luck. Aster mentioned that the card his father was creating would be one of the most powerful ever made. Knowing the money that he could make dueling professionally, The D broke into the Phoenix residence that night to steal the card. The Light of Destruction inside the card influenced him, and he killed Mr. Phoenix in the ensuing struggle. In the English dub, Mr. Phoenix was said to be kidnapped, but his death is still alluded to by The D himself. This leaves his son an orphan, but The D himself adopts Aster in order to cover his trail.

In the next ten years The D, uses the Destiny-altering powers of the Light Destruction to reign as the champion of the Pro League, while Aster grows into a strong duelist who ranks high in the League himself despite only being fifteen. Aster had vowed to find his father's murderer, and duels with "Destiny Heroes" his father created. He knows that when he finds "Plasma", he'll find his father's murder. The D eventually invites Aster to his yacht, and there he reveals the truth and duels Aster. In addition to his winning record in the Pro League, The D had competed in numerous underground duels, where he had used "Plasma" to imprison the souls of countless duelists. The first victim was Mr. Phoenix himself, who briefly communicates with Aster during the duel. He urges his son to win the duel, which would release the souls of the duelists and purify the card. After some hesitation, Aster does so, thrawting The D's strategy via "Destiny Hero - The Dark Angel" and attacking with "Destiny Hero - Celestial" to destroy "Plasma" and win the duel. With this, the soul of Mr. Phoenix is finally able to rest in peace.

Manga
In the manga, Mr. Phoenix is still a card designer, and he created the "Legendary Planets" series. Due to the powers of these cards, he was targeted by Tragoedia, who killed him and stole the cards, with the possible exception of "Elemental Hero Terra Firma". Tragoedia would eventually distribute the cards to students of the American Branch of Duel Academy through Principal MacKenzie.