High Priest Seto

Kaiba's given name, Seto, is the Japanese phonetic equivalent of the ancient Egyptian deity Set, the god of chaos, war and storms in Egyptian mythology. That is for whom he is named. Kaiba is the reincarnation of Priest Seto (a.k.a. Set, sometimes called Seth by fans), the ancient Egyptian Priest from the reign of the Pharaoh Atem, his cousin. He owned the Millennium Rod and was one of the Six High Priests guarding the Millennium Items - Atem holding the Puzzle. Seto rebelled against Atem at one point and lost. However, just before Atem was sealed into the puzzle, he named Seto as heir to the Egyptian Throne. The battle is shown in the stone tablet Ishizu showed Seto (who refused to accept it). The Millennium Rod eventually opened Seto's eyes to accept the truth, though he still has some doubts.

In his past life, it is suspected that Seto either loved or had a deep feeling of friendship for Kisara, a girl with the legendary Blue-Eyes White Dragon as her Ka. Unfortunately, before it became clear which was the case, she died due to his father sealing her Ka into a stone tablet. This helps explain Kaiba's connection with the Blue-Eyes, though only on a superficial basis. Kisara, the original manifestation of the Blue-Eyes, represented sacrifice in that she would help save Priest Seto from the darkness after Seto was possessed by the then evil Akunadin, and then, as the Blue-Eyes White Dragon, serve to protect Priest Seto and the kingdom in the final battle against Thief King Bakura and Zorc.

Present day Seto Kaiba, on the other hand, seemed rather unaffected when he witnessed the death of Kisara when he was inside the Memory World. To him, the Blue-Eyes represented ultimate power and domination in the game of Duel Monsters. And with 3000 ATK, it has remained the strongest monster that can be normal or special summoned with no real drawbacks. And that he carries three of the only four copies in existence further seems to reflect upon not only said near-domination of the game, but also his elite status in everything he does.

In his past life, as Priest Seto, he also seemed to be a more humble, caring human being. His sense of duty prevailed over his ego, and he felt so deeply for Kisara that he actually cried at her death.