Peacemaking is part of the Bard class skill set.
Use of it stops all aggressive actions of the enemies:
Impact on monsters – brings the aggression to the end.
Impact on players – forbids attack and casting spells for 1 second or interrupts an already cast spell.

Skill’s efficiency

The skill is used with the help of musical instruments.
Use the skill to calm your listeners. Keep in mind that this skill affects both monsters and players.

Ways of leveling your Peacemaking

The requirements for Peacemaking to affect monsters are the same as for Provocation:

Use the skill close to monsters that are appropriate to your skill.

Here is a detailed video of how the skill is used: