Shields

"The hero who wields a shield in their off-hand is giving up the capacity to hold killing devices in both hands or carry a power-enhancing item, but choosing to do so can save their life, or at least prolong it a few seconds under a storm of arrows or claws."

- Game Guide^(src)

Shields are an excellent way to improve your defense. Shields increase your defense rating and provide heroes with a chance to block incoming attacks (effectively reducing damage of those attacks by a fixed amount). Some classes, like Paladins and Crusaders, rely more heavily on shields than others.

All shields occupy the off-hand, so equipping a two-handed weapon with a shield is only possible with the Crusader passive skill Heavenly Strength.

Diablo/Hellfire

Shields in Diablo I and Hellfire function at their most basic levels. Unless you have a shield but no melee weapon equipped, you cannot use a shield to damage your enemies. They are best in the hands of a Warrior or a Barbarian wishing to use blunt weaponry, because not only do they possess the natural strength needed to equip the higher end shields, but they naturally possess Fast Block as well. A hero's Chance to Block is not limited by a hard cap, so one could bring their Dexterity high enough to guarantee blocks against melee and ranged attacks.

Diablo I Unique Shields

Split Skull Shield (Buckler) • The Deflector (Buckler) • Blackoak Shield (Small Shield) • Holy Defender (Large Shield) • Dragon's Breach (Kite Shield) • Stormshield (Tower Shield/Gothic Shield)

Diablo II/Lord of Destruction

Shields in Diablo II / Lord of Destruction have some new tricks onto them, compared to Diablo/Hellfire. To name one, there are certain totems only usable by the Necromancer, and there are certain Paladin Shields that only the Paladin can equip. Another example is the Paladin's Smite skill, which allows him to stun and knockback his foes by bashing them with his shield (and cannot be used if no shield is equipped). Chance to Block has a hard cap of 75% when immobile, walking, or attacking, and 25% when running. Having an increase in Dexterity will contribute to a higher block chance, as well as the Paladin's Holy Shield skill.

Diablo II Shields

Normal Shields — Buckler • Small Shield • Large Shield • Kite Shield • Spiked Shield • Tower Shield • Bone Shield • Gothic Shield
Exceptional Shields — Defender • Round Shield • Scutum • Dragon Shield • Barbed Shield • Pavise • Grim Shield • Ancient Shield
Elite Shields — Heater • Luna • Hyperion • Monarch • Blade Barrier • Aegis • Troll Nest • Ward

Diablo II Unique Shields

Normal Shields — Pelta Lunata (Buckler) • Umbral Disk (Small Shield) • Stormguild (Large Shield) • Steelclash (Kite Shield) • Swordback Hold (Spiked Shield) • Bverrit Keep (Tower Shield) • Wall of the Eyeless (Bone Shield) • The Ward (Gothic Shield)
Exceptional Shields — Visceratuant (Defender) • Moser's Blessed Circle (Round Shield) • Stormchaser (Scutum) • Tiamat's Rebuke (Dragon Shield) • Lance Guard (Barbed Shield) • Gerke's Sanctuary (Pavise) • Lidless Wall (Grim Shield) • Radament's Sphere (Ancient Shield)
Elite Shields — Blackoak Shield (Luna) • Stormshield (Monarch) • Spike Thorn (Blade Barrier) • Medusa's Gaze (Aegis) • Head Hunter's Glory (Troll Nest) • Spirit Ward (Ward)

Diablo III

Shields return in Diablo III / Reaper of Souls, but their functions are nerfed down from that of Diablo II / Lord of Destruction. A successful Chance to Block is a bit more difficult to attain, due to the fact that Shields cannot roll higher than 20% Chance to Block without affixes that increase said chance (up to 31% total). They also do not block all damage when they do block an attack. Instead, each shield carries a Block Amount, seen under its Chance to Block. They do, however, contribute the most Armor out of any equipment type, being the only piece able to achieve 1,000 Armor (on level 60) and 2000 Armor (on level 70) without affixes that increase that Armor or Strength.

Shields may also roll reduced damage from elites, bonus damage to elites, reduced damage from melee / ranged attacks, Critical Hit chance, reduced resource costs, increased Life and Life regeneration, increased healing, Thorns, status effect duration reduction, all resistances, a socket, and various 'on hit' effects.

Like Paladins in Diablo II, Crusaders have their own type of shields: Crusader Shields. Some of Crusader skills can only be used with a Shield equipped in the off-hand.