Final answer:
While searching Sirius's bedroom in the Harry Potter series, Harry found a family photo album, which served as an "incredible treasure" to him as it helped him feel closer to his parents and godfather.
Step-by-step explanation:
In the Harry Potter series, while searching Sirius's bedroom, the "incredible treasure" Harry found was not a valuable gemstone, rare book, or magical map, but a family photo album (d). This album was important to Harry as it carries his personal history and relationship with Sirius.Sirius's bedroom was a place where Harry got a more intimate look into his godfather's life. This family photo album provided Harry with a deeper connection to his parents and godfather, helping him to understand them more completely and feel closer to them.
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