Amantius Allectus' diary is located in his house in the Temple District of the Imperial City in The Elder Scrolls IV: Oblivion. Specifically, the diary can be found on a desk on the first floor of his house, which is near the southeast corner of the Temple District, close to the entrance to the Arboretum. The house is the first on the right when leaving the district from the east toward the Arboretum. The door to the house is locked, but it can be lockpicked to gain entry. Once inside, the diary is on a reading desk to the right as you enter

. This diary is a key item for the Thieves Guild quest "May the Best Thief Win," where players compete to steal the diary first to join the guild

. If you fail to get the diary from Amantius' house in time, it may be taken by another thief, Methredhel, who moves it to her shack, where you can steal it later

. In summary, to find Amantius Allectus' diary:

• Go to Amantius Allectus' house in the Temple District of the Imperial City.
• Pick the lock to enter the house.
• Find the diary on the desk on the first floor near the basement door.
• Retrieve it quickly to win the quest and join the Thieves Guild