Armand Christophe in The Elder Scrolls IV: Oblivion can be found primarily in the Waterfront District of the Imperial City. He lives in a small shack there and follows a daily routine involving spending time in his house, strolling around the district, dining at The All-Saints Inn in the Temple District, and meeting at the Garden of Dareloth at night with other Thieves Guild members

. During the quest "The Elven Maiden," Armand goes into hiding because he is accused of stealing a bust from Cheydinhal, which was actually a setup to expose a traitor within the Thieves Guild. While in hiding, you can ask locals in the Waterfront district about his whereabouts, and you will be directed to Methredhel, who will inform you about Armand's situation

. After completing the quest and clearing his name, Armand returns to the Garden of Dareloth at midnight to meet the player and promote them within the Thieves Guild

. Additionally, Armand can sometimes be found in the basement of the Imperial Trading Company Warehouse, especially related to quest events

. In summary, Armand Christophe is mostly located in the Imperial City's Waterfront District, particularly at his shack, The All-Saints Inn, the Garden of Dareloth at night, and occasionally in the Imperial Trading Company Warehouse basement depending on quest progress