Prerequisites: Ability to cast divine spells.

You have the power to affect undead creatures by channeling the power of your faith through your holy (or unholy) symbol (see Turn or Rebuke Undead).

You must choose whether your turning ability channels positive energy or negative energy. Positive energy can turn or destroy undead creatures. Negative energy instead rebukes or commands such creatures. Once this choice is made, it cannot be reversed. This decision also determines whether the cleric can cast spontaneous cure or inflict spells (see above).

You may attempt to turn undead a number of times per day equal to 3 + your Charisma modifier. If you have 5 or more ranks in Knowledge (religion) you get a +2 bonus on turning checks against undead.

Canon

A cleric takes this ability at 1st level, while a paladin on the defensive axis take this ability at 4th level.