The Third Decan of Scorpio

This is the third ten-degree segment of Scorpio, the fixed water sign, spanning 20 to 30 degrees. Its ruler in the Chaldean order of faces is Venus, reached by continuing the planetary sequence around the thirty-six decans. The decan is the oldest layer of astrology, the thirty-six having begun as Egyptian star groups used to divide the year and the night, absorbed into the zodiac as ten-degree arcs only in the last centuries BCE.

The Golden Dawn, from 1888, mapped the numbered minor cards onto the decans in zodiacal order; this segment carries the Seven of Cups, to which they gave the title Debauch, its Venus-in-Scorpio attribution taken from the face ruler, Venus in its detriment in the dark water sign matching the card's images of illusion, glamour and dissipation. That tarot layer is a modern Western overlay on the ancient decan scheme rather than part of the inherited astronomy.