Shields

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Version 0.28: 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 four types of shield, in order of size:

Some magical effects can also increase your SH score.

Shield Penalties

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

Specifically, your shield penalty is 2/5 * encumbrance^2 / (20 - 3 * size_factor) * (27 - shield_skill) / 27[1]. This is your penalty to your evasion, which gets used to calculate everything else. This means that larger species can wield shields more comfortably, while anyone can eliminate shield penalty by maxing out the Shields skill.

Shield type Encumbrance
Buckler 5
Kite shield 10
Tower shield 15
Size Races Size factor
Little Spriggan +4
Small Kobold +2
Normal most races 0
Normal
(strong arms)		 Formicid -2
Large
(normal torso)		 Palentonga, Naga -2
Large Ogre, Troll -2

The shield penalty, in EV, is added to your attack delay, in single aut. This applies to weapons, missiles or unarmed attacks. For non-integer aut penalties, the game will have a weighted roll (rounding up or down) so that the average penalty is the expected delay.[2]

Egos

Bucklers, kite shields, and tower shields can spawn with the following egos[3]:

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

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 are under the effect of a magical shield (amulet of reflection, Qazlal's Storm Shield, or the Shining One's Divine Shield) or have the Large Bone Plates mutation. 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.

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

Some examples of ranged attacks that can be blocked:

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 either of those: 

+ 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), modified by a size factor:

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
  • Stat bonus is DEX * 38 * (base_shield + 13) / 26,
  • 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

  • In 0.28, orbs, magical nonshields in the offhand slot, were introduced.
  • Prior to 0.28, the two larger shields used Strength (along with Dexterity) to determine bonus SH. Shields had a to-hit penalty. The penalty formula changed; before, certain skill thresholds (4 skill for buckler, 15 for kite shield, 25 for tower shield) negated it.
  • 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.

References

  1. ↑ player.cc:5587 (0.28.0)
  2. ↑ player-act.cc:296 (0.28.0)
  3. ↑ makeitem.cc:768 (0.28.0)
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