The Gem of Irresistible Spirit is an essence gem which grants bonuses to Spirit and Charm. It is exclusive to followers of the Way of the Open Palm, but another gem, the Gem of Seductive Power, can provide the same bonuses to a follower of the Way of the Closed Fist.
It is found at random.
In-game description: "This gem is a tool of inner reflection for the wielder and, unwittingly, those around him. This gem exposes the inner strength and virtue of the user to all, awing them with his true nature. Only the most peace with themselves can use this gem, for others will see their own flaws reflected back at them."