From Dungeons of Dredmor Wiki
"Return with your shield - or under it? For the defense-minded adventurer."
Unlike weapon skills, Shield Bearer does not require you to have a shield equipped to receive its full effects and does not grant a double bonus when equipping two shields. It functions identically whether the user is dual wielding weapons, using a weapon and a shield, or using two shields; the character can even use abilites such as Defensive Bash and Tortoise Maneuver with dual weapons.
 Granted Abilities
|Duck and Cover!||-||20 % chance when hit to proc Duck and Cover on the character for 24 turns. It causes the following: +1 +2 -1 -1 +2 +10 +4.|
|Defensive Bash||12||Defensive Bash deals ( 6 + 0.2 ) to a single monster, paralyzes it for 3 turns and knocks it back 1 tile. Has a chance to cause Crushed Bones.|
|Tortoise Maneuver||36||Tortoise Maneuver is an ability that buffs the character with the following effects: +2 -2 +2 +5 +4. It lasts until the character takes 9 hits.|