The official GemStone IV encyclopedia.
Magical shields will not shatter, but their holder will temporarily lose their ability to block.
Weapons that are not suitable for use in executing the sunder shield maneuver include rapiers, whips, daggers, and brawling weapons.
>cman sunder [Roll result: 163 (open d100: 87) Bonus: 1] You swing your vultite handaxe at an Illoke jarl's iron-banded greatshield and connect! The iron-banded greatshield splinters and is rendered utterly useless! Roundtime: 3 sec.
>cman sunder [Roll result: 222 (open d100: 123) Bonus: 3] You swing your vultite maul at a n'ecare's wooden buckler and connect! A n'ecare's wooden buckler emits an awful vibrating clanging sound! Roundtime: 3 sec.