Difference between revisions of "Shields"

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''For the skill, see [[Shields (skill)]]. For the item formerly known as just a shield, see [[kite shield]].''
 
{{flavour|“Let who will boast their courage in the field,<br>
 
{{flavour|“Let who will boast their courage in the field,<br>
 
I find but little safety from my shield.<br>
 
I find but little safety from my shield.<br>
Line 10: Line 11:
 
-Archilochos. 7th cent. B.C. trans. William H. Goodwin, 1878.}}
 
-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. Some other effects can also grant you an SH score.
+
[[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]]
 +
 
 +
[[Orb]]s 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==
 
==Shield Penalties==
Wearing a shield also gives penalties to attack speed, attack damage, and spellcasting, along with EV penalties of -0.8 ([[buckler]]), -3 ([[kite shield]]), or -5 ([[tower shield]]). While the penalty for wearing a small buckler is almost negligible, a tower shield can seriously slow your attacks and make spellcasting unreliable. Sufficient Shields skill will reduce or even negate these penalties. The amount needed varies by race, but can be found in the description of the shield in-game:
+
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.  
  
{| class="prettytable" cellpadding="10" border="9"
+
===EV Penalty===
|- align="center"
+
Your shield EV penalty is <code>2/5 * encumbrance^2 / (20 - 3 * size_factor) * (27 - shield_skill) / 27</code><ref>{{source ref|0.29.1|player.cc|5653}}</ref>. Larger species can wield shields more comfortably, smaller species have more difficulty with shields, and anyone can eliminate shield penalty by maxing out the Shields skill.
! Size !! Races !! Buckler !! Kite shield !! Tower shield
 
|-
 
|Little || [[Spriggan]] || 7.2 || - || -
 
|-
 
|Small || [[Kobold]], [[Halfling]] || 5.6 || 21 || -
 
|-
 
|Normal || most races || 4 || 15 || 25
 
|-
 
|Large (normal torso)<br> & Formicids || [[Palentonga]], [[Naga]], [[Formicid]] || 2.4 || 9 || 15
 
|-
 
|Large || [[Ogre]], [[Troll]] || - || 9 || 15
 
|}
 
  
Your Shield penalty is (Shield EV penalty) - (Shields skill)/(5 + (Size factor)). Shield EV penalty and Size factor can be looked up in these tables:
+
The EV penalty is subtracted directly from your evasion, and is used to calculate the other penalties.
  
 
{| class="prettytable" cellpadding="10" border="9"
 
{| class="prettytable" cellpadding="10" border="9"
 
|- align="center"
 
|- align="center"
! Shield type !! Shield EV penalty
+
! Shield type !! Encumbrance
 
|-
 
|-
|Buckler || -0.8
+
|Buckler || 5
 
|-
 
|-
|Kite shield || -3
+
|Kite shield || 10
 
|-
 
|-
|Tower shield || -5
+
|Tower shield || 15
 
|}
 
|}
  
Line 49: Line 46:
 
|Little || [[Spriggan]] || +4  
 
|Little || [[Spriggan]] || +4  
 
|-
 
|-
|Small || [[Kobold]], [[Halfling]] || +2
+
|Small || [[Kobold]] || +2
 
|-
 
|-
|Normal || most races || 0
+
|Normal || most species || 0
 
|-
 
|-
|Large<br>(normal torso) & Formicids || [[Centaur]], [[Naga]], [[Formicid]] || -2
+
|Normal<br>(strong arms)||[[Formicid]] || -2
 +
|-
 +
|Large<br>(normal torso)|| [[Palentonga]], [[Naga]]|| -2
 
|-
 
|-
 
|Large || [[Ogre]], [[Troll]] || -2
 
|Large || [[Ogre]], [[Troll]] || -2
 
|}
 
|}
  
When attacking with any kind of weapon (including unarmed), if you are wearing a shield and your Shield penalty is greater than zero, the game throws two dice with (Shield penalty) sides. The smaller value rolled is added to your attack delay.
+
===Attack Penalty===
 +
The shield penalty, in EV, is added to your attack delay, in single [[aut]]s. This applies to weapons, missiles, and 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.<ref>{{source ref|0.29.1|player-act.cc|306}}</ref>
 +
 
 +
===Spell Penalty===
 +
The spellcasting penalty is significantly more complicated. Shields add to the raw spell failure rate, in % failure:
 +
 
 +
<code>spell failure = 19 * [ev_penalty - ( (shields_skill) / (Size factor + 5) )] </code>
 +
 
 +
This is then modified by various functions described in the [[spell success]] page.
  
 
==[[Ego]]s==
 
==[[Ego]]s==
All three types of shields can spawn with the following egos<ref>{{source ref|0.25.0|makeitem.cc|806}}</ref>:
+
[[Buckler]]s, [[kite shield]]s, and [[tower shield]]s can spawn with the following egos<ref>{{source ref|0.29.1|makeitem.cc|741}}</ref>:
 
*~3%, [[Resistance_(ego)|resistance]]
 
*~3%, [[Resistance_(ego)|resistance]]
 
*10%, [[fire resistance]]
 
*10%, [[fire resistance]]
Line 70: Line 77:
 
*39%, [[protection]]
 
*39%, [[protection]]
  
Shields of [[cold resistance|cold]] and [[fire resistance]] can occasionally be found in [[ice cave]]s and [[volcano]]es.
+
Shields of [[cold resistance|cold]] and [[fire resistance]] can also occasionally be found in [[ice cave]]s and [[volcano]]es, respectively.
 +
 
 +
Every [[orb]] has its own ego; see the [[orb]] page for more details.
  
 
==Blocking==
 
==Blocking==
 
===Effect===
 
===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 [[Good_mutations#Large_Bone_Plates|Large Bone Plates]] mutation. Your ability to block missiles doesn't benefit from [[Repel Missiles|missile-repelling]] effects like a [[scarf]] of repulsion, and you cannot benefit from any form of shield while you are [[confuse]]d.
+
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 [[Repel Missiles|missile-repelling]] effects like a [[scarf]] of repulsion, and you cannot benefit from any form of shield while you are [[confusion|confused]], [[held]], [[paralyzed]], or [[petrified]].
  
 
All melee attacks can be blocked (except for successful [[stab]]s), but many ranged attacks are unblockable:
 
All melee attacks can be blocked (except for successful [[stab]]s), but many ranged attacks are unblockable:
*Bolt spells: [[Starburst]], [[Lightning Bolt]], [[Bolt of Magma]], [[Shock]], and [[Searing Ray]]
+
*[[Penetration|Penetrating]] attacks: [[Javelin]]s, [[Bolt spell]]s, [[Starburst]]...
*Explosions: [[Fireball]], [[Damnation]], [[Fire Storm]], [[Conjure Ball Lightning]], [[Lee's Rapid Deconstruction]], [[exploding (brand)|exploding]]-branded weapons
+
*Explosions: [[Fireball]], [[Lee's Rapid Deconstruction]], [[Damnation]]...
 
*Electrical discharges: [[Static Discharge]], [[Chain Lightning]]
 
*Electrical discharges: [[Static Discharge]], [[Chain Lightning]]
*Enchantments: [[Agony]], [[Pain]], [[Confuse]], [[Mesmerise]], etc
+
*Enchantments: [[Agony]], [[Pain]], [[Confuse]], everything that checks [[willpower]]
*Beams with perfect accuracy: [[Magic Dart]], [[Sticky Flame]] (only the player's version)
+
*Beams with perfect accuracy: [[Magic Dart]], [[Freeze]], [[Smite]]...
*Other ranged attacks that are not beams: [[Shatter]], [[Tornado]], [[Airstrike]], [[Smite]], [[Ozocubu's Refrigeration]], [[Freeze]], etc
+
*Other ranged attacks that are not beams: [[Shatter]], [[Polar Vortex]], [[Ozocubu's Refrigeration]]
*[[Penetration]]-branded weapons (primarily [[javelin]]s)
 
  
 
Some examples of ranged attacks that can be blocked:
 
Some examples of ranged attacks that can be blocked:
*Ranged weapons like [[Bows]] or [[Slings]]
+
*Ranged weapons like [[shortbow]]s and [[sling]]s
*Spells that fire projectiles like [[Iron shot]], [[Poison Arrow]], [[Orb of Destruction]], [[Lehudib's Crystal Spear]], [[Throw Icicle]], [[Stone Arrow]], [[Throw Flame]], [[Throw Frost]], [[Sting]], [[Sandblast]]
+
*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.  
+
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===
 
===Calculation===
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  + min(0.38×Shield skill, .57 + 0.19×Shield skill)
 
  + min(0.38×Shield skill, .57 + 0.19×Shield skill)
  
or [[Helm card]] (this does not stack with a physical shield):
+
and then on top of this:
SH = 4.5 + 0.375×[[Invocations]]
 
 
 
and then on top of either of those:
 
 
  + Divine shield bonus
 
  + Divine shield bonus
 
  + Qazlal shield bonus
 
  + Qazlal shield bonus
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|Little || [[Spriggan]] || +2 || - || -
 
|Little || [[Spriggan]] || +2 || - || -
 
|-
 
|-
|Small || [[Kobold]], [[Halfling]] || +1 || +0.5 || -
+
|Small || [[Kobold]] || +1 || +0.5 || -
 
|-
 
|-
 
|Normal || most races || 0 || 0 || 0
 
|Normal || most races || 0 || 0 || 0
 
|-
 
|-
|Large<br>(normal torso) & Formicids || [[Centaur]], [[Naga]], Formicid || 0 || 0 || 0
+
|Normal<br>(strong arms)|| [[Formicid]] || 0 || 0 || 0
 
|-
 
|-
|Large || [[Ogre]], [[Troll]] || - || -0.5 || 0
+
|Large<br>(normal torso)|| [[Palentonga]], [[Naga]] || 0 || 0 || 0
 +
|-
 +
|Large
 +
|| [[Ogre]], [[Troll]] || - || -0.5 || 0
 
|}
 
|}
  
*'''Stat bonus''' is 38×DEX for bucklers, 19×STR + 19×DEX for kite shields, or 26×STR + 12×DEX for tower shields. Then this value is multiplied by (block + 13)/26, and by 100.
+
*'''Stat bonus''' is <code>DEX * 38 * (base_shield + 13) / 5200</code><ref>{{source ref|0.29.1|player.cc|2149}}</ref>,
 
 
 
*The Shining One's '''Divine shield bonus''' is based on Invocations skill.
 
*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 [[Good_mutations#Large_Bone_Plates|Large Bones Plates]] mutation.
 
*'''Mutation bonus''' is +4/6/8 SH depending on your level of the [[Good_mutations#Large_Bone_Plates|Large Bones Plates]] mutation.
  
 
The resulting value is rounded to the nearest integer and displayed as the player's SH value.
 
The resulting value is rounded to the nearest integer and displayed as the player's SH value.
 
For reference, a 15-Dex, 15-Str character wearing a buckler has an average blocking value of:
 
*3 with a Shield Skill of 0
 
*6 with a Shield Skill of 8
 
*8 with a Shield skill of 15
 
*11 with a Shield skill of 27
 
 
With a large shield, it becomes:
 
*11 with a Shield Skill of 0
 
*15 with a Shield Skill of 8
 
*19 with a Shield skill of 15
 
*25 with a Shield skill of 27
 
  
 
The attacker's pierce value is equal to:
 
The attacker's pierce value is equal to:
Line 155: Line 149:
  
 
The defender's blocking value is equal to:
 
The defender's blocking value is equal to:
  2d(2×SH)/6 - 1.3 (Divided by 3 against melee attacks from invisible opponents)
+
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.
 
If this value is greater or equal than the attacker's pierce value, the attack is blocked.
  
 
==History==
 
==History==
*In [[0.28]], the shield penalty formula will be changed yet again; it will take 27 skill to remove the penalty entirely.
+
*In [[0.28]], magical [[orb]]s were added as a new category of off-hand equipment.
*In [[0.27]], the shield penalty will increase.
+
*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 shield]]s were known as just "shields" and [[tower shield]]s were called "large shields".
 
*Prior to [[0.25]], [[kite shield]]s were known as just "shields" and [[tower shield]]s were called "large shields".
 
*Prior to [[0.17]], [[unarmed]] attacks had a speed penalty when attacking with a shield equipped.
 
*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 were more complex.
+
*Prior to [[0.16]], the amount of skill required to negate penalties for wearing a shield was more complex.
  
 
==References==
 
==References==
 
<references/>
 
<references/>
 +
 +
{{armours}}
  
 
[[Category:Items]]
 
[[Category:Items]]
 
[[Category:Shields]]
 
[[Category:Shields]]
[[Category:Crystal Ball Articles]]
 

Revision as of 04:59, 22 February 2023

Version 0.29: 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:

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 2/5 * encumbrance^2 / (20 - 3 * size_factor) * (27 - shield_skill) / 27[1]. Larger species can wield shields more comfortably, smaller species have more difficulty with shields, and anyone can eliminate shield penalty by maxing out the Shields skill.

The EV penalty is subtracted directly from your evasion, and is used to calculate the other penalties.

Shield type Encumbrance
Buckler 5
Kite shield 10
Tower shield 15
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

Attack Penalty

The shield penalty, in EV, is added to your attack delay, in single auts. This applies to weapons, missiles, and 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]

Spell Penalty

The spellcasting penalty is significantly more complicated. Shields add to the raw spell failure rate, in % failure:

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

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]:

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:

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 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), 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) / 5200[4],
  • 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, magical orbs were added as a new category of off-hand equipment.
  • 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

Armour
Body Armour Leather armourRing mailScale mailChain mailPlate armourCrystal plate armour

RobeAnimal skinTroll leather armourSteam dragon scalesAcid dragon scales
Swamp dragon scalesQuicksilver dragon scalesFire dragon scalesIce dragon scales
Pearl dragon scalesShadow dragon scalesStorm dragon scalesGold dragon scales

Miscellaneous HatHelmetCloakScarfGlovesBootsBarding
Shields BucklerKite shieldTower shieldOrb