Forbidden Speech

5th-level enchantment
Casting Time: 1 minute
Range: Touch
Components: V, S
Duration: Permanent
Book of Vile Darkness

You make it impossible for the target to speak about a certain topic of your choosing. Topics must be specific, such as time spent in captivity, or what they saw over the past 10 minutes. Invalid topics include verbal spellcasting components, a creature’s life history, etc.

The target  makes an Intelligence saving throw or is subject to the spell. They still remember the topic, but have no way of communicating information about it. Words become gibberish, drawings or writings are too messy to make out, gestures are too erratic, and even thoughts are too muddled to understand via telepathy.

This spell’s effects can be removed or healed with greater restoration or similar magic.
 
 
At Higher Levels: When you cast this spell using a spell slot of 6th level or higher, its effects can only be removed if greater restoration or similar magic is cast at the same level or higher.**

Forbidden Speech

5th level Corrupt enchantment spell.
Casting time 1 minute.
Touch range.
Components V, S.
Duration permanent. 
Book of Vile Darkness

The caster makes it impossible for a single creature to speak about a single topic if the creature fails a WIS save. The topic should be as narrow as possible for the spell to work properly. An appropriate topic might be events that occurred while the creature was in captivity, the whereabouts and names of tormentors, the secret location of a hidden treasure, the password into a guarded compound, the command word of a magic item, or the explanation behind some major occurrence. Invalid topics include verbal components of spells, a creature's whole life history, or anything too broad for a reasonable definition of a single topic. Whether a topic is too broad is up the DM, who can double the corruption cost and have the spell automatically fail if the caster persists in attempting an invalid topic. Thus, this can be a dangerous spell to attempt. The affected creature cannot communicate regarding the topic in any way. Speech becomes gibberish, writing is reduced to an indecipherable scrawl, gestures are impossible, and even telepathy (including detect thoughts) is scrambled. The creature has not forgotten the information, however, and it can be a maddening occurrence for the creature to be unable to communicate information that might be of life-and-death importance to friends and allies.

Corruption Cost: 1d6 STR damage

Any spellcaster that prepares spells can learn these spells. Each spell list has an alignment attached to it. If a creature of a different alignment casts one of these powerful spells, their alignment shifts towards the alignment of the spell by one step. Each spell has a corruption cost that is paid when the duration of the spell ends or according to the spell’s description. If the cost is ability damage, it is restored when the caster finishes a long rest. If the cost is ability drain, it does not recover until the creature receives attention from a Greater Restoration spell.