Pisces rising places Pisces on the eastern horizon at birth, and the Ascendant changes sign about every two hours, so a birth time is required. In whole-sign houses, where each sign is one house, Pisces is the first house. Jupiter, Pisces's traditional ruler, is the lord of the Ascendant; modern astrologers add Neptune, which this block leaves out. Jupiter also rules Sagittarius, in the tenth house. Pisces is a feminine, mutable water sign, and Venus is exalted there while Mercury is in fall and in detriment, a concept the tradition names explicitly only late. Jupiter is a benefic and belongs to the day team, a grouping called sect that sorts planets by day and night charts. Hellenistic astrologers therefore look at where Jupiter is by sign and house, and whether the chart was born by day, when Jupiter is in sect.
A note on “detriment”: the early Hellenistic texts note a planet opposite its own sign without naming it. The term is defined only in late and medieval sources, and scholars disagree on whether the idea was implicit earlier.