Pegasus' diary

Pegasus' diary was a book in the anime, Maximillion Pegasus wrote explaining why he created Duel Monsters. He left it in for the winner of the Duelist Kingdom tournament to read. In the manga, the diary did not exist and Pegasus told everything in it directly to Yugi.

Contents
The beginning of the diary address the new King of Duelists. (In the English version, it addresses Cecelia.)

It explains that Cecelia was Pegasus' lover, who died when she was 17 and the two had met at a party in Las Vegas held by Pegasus' father, 14 years prior to when the diary was written. They were attracted to each other and told each other their dreams. Pegasus' being that he wanted to be a painter and travel the world. The two vowed to always be together. However tragedy struck and Cecelia died of an illness. (In the English version, it also says that Pegasus and Cecelia got married and the day that Cecelia agreed to marry him was the happiest day of his life.)

Pegasus wrote that he went to Egypt to study reincarnation in the hope of seeing Cecelia again. (In the English version, he said he was determined to search the Earth for a way to reach her beyond the mortal veil and his travels led him to Egypt.) Here he met Shadi, who knew what Pegasus was going through, but told him to leave. However Pegasus followed to an underground cavern. However the guards spotted him and took him to Shadi, who was guardian of the Millennium Items. Explaining that the only way to leave the crypt is to be chosen, Shadi inserted the Millennium Eye into Pegasus left socket, saying it would either choose him and give him and grant his wish or punish him for being unworthy. The eye choose Pegasus and for a brief moment, he was reunited with a vision of Cecelia. Seeing her was not the same as touching her, but Pegasus was inspired to find away to hold her again.

Events
After the Duelist Kingdom tournament, Yugi Muto inquired about the souls of Grandpa, Mokuba Kaiba and Seto Kaiba, who Pegasus had promised to free. However Pegasus was unavailable to talk having been attacked by Yami Bakura. Yugi, Joey Wheeler, Téa Gardner, Tristan Taylor and Ryo Bakura then went to the sanctuary in Pegasus' castle, where they found the diary and the "Cecelia Pegasus" card inside it.

The diary was written in English, whereas Yugi and his friends were Japanese. However Téa was able to translate it. (This detail is omitted in the English version, as the characters are always shown speaking English.) They empathized a bit with Pegasus after reading it.