A slaver is a villain who treats individuals like property and forces them into cruel, unfair and iniquitous labor, whether by driving them into slavery by force, buying or selling them on the black market, abducting them or threatening them with torture and death.

This can also apply to characters who force individuals into submission via mind-control, magic or other means - these villains tend to fall under the Neutral Evil and/or Lawful Evil alignment, but some villains who are Chaotic Evils also enslave others if they find it amusing.