This plain gold band has two different effects. When worn by most characters it simply gives a +1 on all saving throws vs. undead and their effects; +1 vs. Ghast stink; +1 to save vs. Vampire charm, etc.
Its full powers are only seen when worn by a cleric or paladin. When such characters wear the Ring of Warding it has the following effects; the wearers acts as if one level higher when attempting to turn undead; if the wearer succeeds in turning undead an additional 1d4 undead are turned or destroyed and the undead are turned for maximum duration; the wearer has +1 A.C. vs undead and makes all saving throws vs magical or poison effects of the undead at +1; if an effect generated by an undead normally has no saving throw the Ring of Warding grants a save of 20 which can be modified by magic, etc.
Example; Aurelius the Studious, a cleric, is 8th level and wears a Ring of Warding. He is traveling deep into a cavern system in hopes of destroying a hidden temple to the Ghoul God said to be hidden there when he and his companions are attacks by a horde of 17 wights! Gripping his crucifix firmly he raises it high and calls out,
"Deus te Perdat!"
He then rolls to turn undead but uses the chart for 9th level clerics, not 8th. This means that instead of automatically turning some of the wights he now destroys them! In addition to the normal 2d6 he adds 1d4 getting a lucky total of 13, meaning only 4 remain.
The wights close so quickly he has to get his mace into his hands immediately as they fall upon the party. Doomsman the barbarian and the Amazon dealt with two of the fell creatures quickly and Jonas was holding his own but the one attacking Aurelius, perhaps by luck, perhaps by fierceness, lunged forward and touched him, trying to leech out his lifeforce.
Normally level drain has no save, but the Ring of Warding gives Aurelius a based save of 20. He is also wearing a +3 Amulet of Protection and is under the effects of a Prayer spell he cast earlier, so he needs 16 or better to save. He rolls an 18 and handily avoids losing a level.