The Magi Crown does affect your willpower (specifically, it gives +5 to intelligence and -10 to willpower).
Due to the way I originally programmed things (and later on, some conflicts between third-party scripts) the values don't update right away, but only after you exit and then re-enter the menu when it comes to equipment affecting your personal stats.
For the pendant, do you mean the Marintas's? If so, that one unlocks all unique hypno-themed scenes around the game. If you are talking about the weird pendant, you can take it off at will, if I remember right. That one affects wet dreams you get if you take a nap (higher slut reputation values unlock more scenes).