The Gem of Seductive Power is an essence gem which grants bonuses to Spirit and Charm. It is exclusive to followers of the Way of the Closed Fist, but another gem, the Gem of Irresistible Spirit, can provide the same bonuses to a follower of the Way of the Open Palm.
In-game description: "People of negotiable virtue can often be overwhelming in their advances. No small thanks for that go to this gem. Nicknamed a Woman's Best Friend, it gives the user power a courtesan would kill for. All are drawn to the power and passion of the wielder, doing his or her decadent bidding."