Target 1 "Libromancer" monster you control and 1 monster your opponent controls; return your monster to the hand, and if you do, take control of that opponent's monster. If your "Libromancer" monster you targeted was not a Ritual Monster, the monster you took control of returns to the hand during the End Phase. You can only activate 1 "Libromancer Displaced" per turn.
When your opponent activates a card or effect: Target 1 "Libromancer" Ritual Monster you control; return it to the hand, and if you do, negate that activated effect, then you can Special Summon 1 "Libromancer" monster from your hand or GY. You can only activate 1 "Libromancer Intervention" per turn.
If you control a "Libromancer" monster: You can target 1 face-up monster your opponent controls; this turn, that face-up monster cannot be used as material for a Fusion, Synchro, Xyz, or Link Summon. You can only use this effect of "Libromancer Prevented" once per turn. Once per turn, during the End Phase, if you control no "Libromancer" Ritual Monsters: Send this card to the GY.