To succeed, a cleric must eschew all other action in a given round in order to will an undead creature to fall back and give ground. The cleric must be within 60 feet (12 combat hexes) of the creature to be turned. During the turning attempt, the cleric cannot move or take any other action. Turning undead does not require concentration, however, and the effect occurs at the end of all action on the cleric's side (before the enemy's next action).
The cleric then throws a d20 upon the table below, to determine success. Note that success is no longer measured by the cleric's level, but instead the cleric's knowledge of dweomercraft.
The number indicates the minimum that must be rolled in order to turn the undead creature. Failure to succeed does not mean that the cleric cannot attempt to turn the creature the following round. However it does mean that for that round, the cleric attempt has no effect whatsoever.
Where a 'T' is shown, the cleric does not need to roll; the undead is automatically turned if the cleric wills it. A 'D' indicates that the cleric is able to destroy the creature, banishing it to the lower planes.
A successful turn indicates that the cleric has literally lifted and hurled the creature back a distance of ten feet (2 combat hexes). The creature is then considered 'stunned' and unable to take any aggressive action. The cleric can attempt to turn creatures again and again, driving them back into rooms, causing them to plunge from high places, even pushing non-corporeal creatures through solid walls.
However, it must be noted that undead creatures with average intelligence or more (greater undead) can choose to flee - dissipating if possible, but through whatever means is available. Note that all greater undead will retreat the moment they encounter a cleric that is able to turn them automatically; if the cleric must roll a die, the creature must make an intelligence check before it decides to flee.
The maximum undead that can be affected will be one creature +1 HD per level of the cleric. A first level cleric would be able to affect up to two skeletons, but it would require a 3rd level cleric to turn two shadows (3 HD).