Shields

Version 0.30: This article may not be up to date for the latest stable release of Crawl.

For the skill, see Shields (skill). For the item formerly known as just a shield, see kite shield.

“Let who will boast their courage in the field, I find but little safety from my shield. Nature's, not honour's, law we must obey: This made me cast my useless shield away, And by a prudent flight and cunning save A life, which valour could not, from the grave. A better buckler I can soon regain; But who can get another life again?” -Archilochos. 7th cent. B.C. trans. William H. Goodwin, 1878.

Shields are a kind of armour worn on one hand, preventing the use of two-handed weapons; they make use of the Shields skill. Unlike other armour, shields increase a character's SH defense, giving you a chance at blocking physical (and some magical) attacks entirely. There are three types of shield, from smallest to largest:

• Buckler
• Kite shield
• Tower shield

Orbs also occupy your off-hand slot, but provide no shielding, instead granting assorted magical effects from their special egos.

Some magical effects can also increase your SH score.

Shield Penalties

Wearing a shield imposes penalties to attack speed, EV, and spellcasting. While the penalty for wearing a buckler is almost negligible, a tower shield can seriously slow your attacks and make spellcasting unreliable.

EV Penalty

Your shield EV penalty is equal to:

Stronger characters are less encumbered by shields, and anyone can eliminate shield penalty by maxing out the Shields skill.

Shield type	Encumbrance
Buckler	5
Kite shield	10
Tower shield	15

The EV penalty is subtracted directly from your evasion. Your unrounded EV penalty is also used to calculate the other penalties.

Attack Penalty

The shield penalty, in units of EV, is converted into attack delay, in units of aut.

When you attack with a shield, it'll take 1d(EV_penalty) aut longer. This applies to weapons, missiles, and unarmed attacks. For non-integer EV penalties, it is rounded in a weighted manner before the attack penalty is calculated.

Spell Penalty

The spellcasting penalty is significantly more complicated. Shields add to "SpellFailure", not to be confused with your actual % chance of failure:

spell failure = 19 * [ev_penalty - ( (shields_skill) / (Size factor + 5) )]

Size factor is determined by species:

Size	Races	Size factor
Little	Spriggan	+4
Small	Kobold	+2
Normal	most species	0
Normal (strong arms)	Formicid	-2
Large (normal torso)	Armataur, Naga	-2
Large	Ogre, Troll	-2

This is then modified by various functions described in the spell success page.

Egos

Bucklers, kite shields, and tower shields can spawn with the following egos:

• ~3%, resistance
• 10%, fire resistance
• 10%, cold resistance
• 10%, poison resistance
• 10%, positive energy
• 19%, reflection
• 39%, protection

Shields of cold and fire resistance can also occasionally be found in ice caves and volcanoes, respectively.

Every orb has its own ego; see the orb page for more details.

Blocking

Effect

It's possible to block a melee attack or a ranged projectile attack if you wear a shield of some kind, or otherwise have SH. Your ability to block missiles doesn't benefit from missile-repelling effects like a scarf of repulsion, and you cannot benefit from any form of shield while you are confused, held, paralyzed, or petrified.

All melee attacks can be blocked (except for successful stabs), but many ranged attacks are unblockable:

• Penetrating attacks: Javelins, Bolt spells, Starburst...
• Explosions: Fireball, Lee's Rapid Deconstruction, Damnation...
• Electrical discharges: Static Discharge, Chain Lightning
• Enchantments: Agony, Pain, Confuse, everything that checks willpower
• Beams with perfect accuracy: Magic Dart, Freeze, Smite...
• Other ranged attacks that are not beams: Shatter, Polar Vortex, Ozocubu's Refrigeration

Some examples of ranged attacks that can be blocked:

• Ranged weapons like shortbows and slings
• Spells that fire single-target projectiles like Iron Shot, Poison Arrow, Orb of Destruction, Sandblast

If the attacker's pierce value is less than the defender's blocking value (see below for details), the attack does no damage. Shield blocking is done before rolling your evasion or your AC, but if you have already blocked some attacks in that turn, your blocking ability will be decreased greatly.

Calculation

The defender's blocking value depends on the nature of the shield:

Physical shields:

SH = Block × (1 + Shield skill/40)
+ Enchantment bonus + Stat bonus 
+ min(0.38×Shield skill, .57 + 0.19×Shield skill)

and then on top of this:

+ Divine shield bonus
+ Qazlal shield bonus
+ Mutation bonus
+ Amulet of reflection bonus
+ Any SH bonus from artifacts

For a physical shield (Buckler, Kite Shield, and Tower Shield), Block is the shield's blocking value, equal to the base shield bonus (3 for Buckler, 8 for Kite Shield, 13 for Tower Shield).

• Stat bonus is DEX * 38 * (base_shield + 13) / 5200,
• The Shining One's Divine shield bonus is based on Invocations skill.
• Mutation bonus is +4/6/8 SH depending on your level of the Large Bones Plates mutation.

The resulting value is rounded to the nearest integer and displayed as the player's SH value.

The attacker's pierce value is equal to:

1d(15 + to hit/2 + 5×past_blocks^2) - 1 (melee attacks)

1d(1.3×to hit    + 5×past_blocks^2) - 1 (ranged attacks)   

"To hit" is the monster's To hit value (based primarily on the monster's HD, type, and weapon accuracy) and "past_blocks" is the number of attacks already successfully blocked in the current turn.

The defender's blocking value is equal to:

2d(2×SH)/6 - 1.3 (Divided by 3 against melee attacks from invisible opponents)

If this value is greater or equal than the attacker's pierce value, the attack is blocked.

History

• Prior to 0.30, species size impacted shield encumbrance and SH score. Larger species would be encumbered less by shields, but receive slightly less SH from larger shields. Smaller species were the opposite.
• In 0.28, magical orbs were added as a new category of off-hand equipment.
• Prior to 0.28, shields had a different penalty formula. Before, certain skill thresholds (regular size species: 4 skill for buckler, 15 for kite shield, 25 for tower shield) negated it. They also had a to-hit penalty. In addition, the two larger shields used Strength (along with Dexterity) to determine bonus SH.
• In 0.27, the shield penalty was increased.
• Prior to 0.25, kite shields were known as just "shields" and tower shields were called "large shields".
• Prior to 0.17, unarmed attacks had a speed penalty when attacking with a shield equipped.
• Prior to 0.16, the amount of skill required to negate penalties for wearing a shield was more complex.

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Before 0.30, species encumbrance was reduced by 1 / (20 - 3 * size_factor), instead of the current 1/(5 + strength).

Given the following size factors:

Size	Races	Size factor
Little	Spriggan	+4
Small	Kobold	+2
Normal	most species	0
Normal (strong arms)	Formicid	-2
Large (normal torso)	Palentonga, Naga	-2
Large	Ogre, Troll	-2

Species also had a SH offset. This was added/subtracted before the bonuses from dexterity and shield skill.

Size	Races	Buckler	Kite Shield	Tower shield
Little	Spriggan	+2	-	-
Small	Kobold	+1	+0.5	-
Normal	most races	0	0	0
Normal (strong arms)	Formicid	0	0	0
Large (normal torso)	Palentonga, Naga	0	0	0
Large	Ogre, Troll	-	-0.5	0