Shields

Version 0.12: This article may not be up to date for the latest stable release of Crawl.

Shields are a kind of armour worn in one hand, preventing the use of two handed weapons, which use 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. Certain spells can also grant you an SH score.

Shield Penalties

Wearing a shield also gives penalties to attack speed, attack damage, and spellcasting, along with EV penalties of -1 (buckler), -3 (shield), or -5 (large shield). While the penalty for wearing a small buckler is almost negligible, a large shield can seriously slow your attacks and make spellcasting unreliable. Sufficient Shields skill will reduce or even negate these penalties, but the amount needed varies by race:

Size	Races	Buckler	Shield	Large shield
Little	Spriggan	9	-	-
Small	Kobold, Halfling	7	21	-
Normal	most races	5	15	25
Large (normal torso)	Centaur, Naga	3	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:

Shield type	Shield EV penalty
Buckler	-1
Shield	-3
Large shield	-5

Size	Races	Size factor
Little	Spriggan	+4
Small	Kobold, Halfling	+2
Normal	most races	0
Large (normal torso)	Centaur, Naga	-2
Large	Ogre, Troll	-2

If you are wearing a shield, wielding a one-handed weapon, and your Shield penalty is greater than zero, the game throws two dices with (Shield penalty) sides. The smaller one is added to your delay.

The penalty for unarmed combat is like the penalty for one-handed weapons, but your delay is increased by one aut, 50% of the time, regardless of your Shield penalty.

If you are wearing a 0 EVP armour, you need less shield skill to eliminate just the casting penalties:

Size	Races	Buckler	Shield	Large shield
Little	Spriggan	1.53	-	-
Small	Kobold, Halfling	1.19	15.19	-
Normal	most races	0.85	10.85	20.85
Large (normal torso)	Centaur, Naga	0.51	6.51	12.51
Large	Ogre, Troll	-	6.51	12.51

Blocking

Effect

It's possible to block a melee attack if you wear a shield of some kind or are under the effect of a magical shield (the Helm card's Magic Shield, the Ice Magic spell Condensation Shield, or the Shining One's Divine Shield). Ranged attacks can be blocked only with physical shields, like bucklers, shields, large shields or the Large Bones Plates mutation. The Shining One's Divine Shield will only help you block missiles if you already have a physical shield of some kind. Your ability to block missiles doesn't benefit from spells like Repel Missiles or Deflect Missiles. If the attacker's pierce value is less than the defender's blocking value, 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.

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

• Bolt spells: Bolt of Fire, Bolt of Cold, Lightning Bolt, Bolt of Draining, Venom Bolt, Bolt of Magma, Bolt of Inaccuracy, Shock
• Explosions: Fireball, Hellfire, Fire Storm, Ice Storm, Conjure Ball Lightning, Lee's Rapid Deconstruction, exploding-branded weapons
• Other electricity-based beams: Chain Lightning
• Enchantments: Agony, Pain, etc
• Beams with perfect accuracy: Magic Dart, Sticky Flame (only the player's version)
• Other ranged attacks that are not beams: Shatter, Tornado, Airstrike, Smite, Ozocubu's Refrigeration, Freeze, etc

Some examples of ranged attacks that can be blocked: Iron shot, Poison Arrow, Orb of Destruction, Lehudib's Crystal Spear, Iskenderun's Mystic Blast (the explosion is special), Throw Icicle, Stone Arrow, Throw Flame, Throw Frost, Flame Tongue, Sting, Sandblast

Calculation

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

• Physical shields:

SH = Block × (1 + Shield skill/20 + Racial bonus/30)
+ Enchantment bonus + Stat bonus 
+ Divine shield bonus (this bonus also works without a shield)
+ min(0.76×Shield skill, 1.14 + 0.38×Shield skill) (added only if the sum of the previous terms is > 0)
+ Mutation bonus 

• Helm card:

SH = 9 + 0.75×Evocations
+ Divine shield bonus + Mutation bonus

• Condensation shield (stacks with the Helm card)

SH = 8 + 0.60×Ice magic
+ Divine shield bonus + Mutation bonus

For a physical shield (Buckler, Shield and Large Shield), Block is the shield's blocking value, equal to the base shield bonus (3 for Buckler, 8 for Shield, 13 for Large Shield), modified by a size factor:

Size	Races	Buckler	Shield	Large shield
Little	Spriggan	+2	-	-
Small	Kobold, Halfling	+1	+0.5	-
Normal	most races	0	0	0
Large (normal torso)	Centaur, Naga	0	0	0
Large	Ogre, Troll	-	-0.5	0

• Racial bonus is +4 (+13%) for dwarven shields (+8 (+26%) for dwarves), by +2 (+7%) for elves wearing elven shields and by +4 (+13%) for orcs wearing orcish shields (up to +9 (+30%) for high-piety followers of Beogh).

• Stat bonus is 0.38×DEX for bucklers (you get +1SH for every 2.6 points of DEX) , 0.19×STR + 0.19×DEX for shields (you get +1SH for every 5.3 points of DEX or STR), and 0.26×STR + 0.12×DEX for large shields (you get +1SH for every 3.9 points of STR or 8.3 points of DEX).

• The Shinining One's Divine shield bonus is 4.5 + 0.3×Shield skill. Your stat bonus will be increased to (9 + 0.6×Shield skill) if it was smaller.

• Mutation bonus is +2 SH per every level of the Large Bones Plates mutation.

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:

• 7 with a Shield Skill of 0
• 13 with a Shield Skill of 8
• 16 with a Shield skill of 15
• 23 with a Shield skill of 27

With a large shield, it becomes:

• 22 with a Shield Skill of 0
• 31 with a Shield Skill of 8
• 38 with a Shield skill of 15
• 51 with a Shield skill of 27

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.