Shields

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“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. Some other effects 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 -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:

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)
& Formicids 		Centaur, 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:

Shield type Shield EV penalty
Buckler -0.8
Kite shield -3
Tower shield -5
Size Races Size factor
Little Spriggan +4
Small Kobold, Halfling +2
Normal most races 0
Large
(normal torso) & Formicids 		Centaur, Naga, Formicid -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.

Egos

All three types of shields could spawn with the following egos[1]:

Shields of cold and fire resistance could be often found in ice caves and volcanoes.

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: ranged weapons like Bows or Slings, Iron shot, Poison Arrow, Orb of Destruction, Lehudib's Crystal Spear, Throw Icicle, Stone Arrow, Throw Flame, Throw Frost, Sting, 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)

or Helm card (this does not stack with a physical shield): 

SH = 4.5 + 0.375×Invocations

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, 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) & Formicids 		Centaur, Naga, Formicid 0 0 0
Large Ogre, Troll - -0.5 0
  • Stat bonus is 38×DEX for bucklers, 19×STR + 19×DEX for shields, or 26×STR + 12×DEX for large shields. Then this value is multiplied by (block + 13)/26, and by 100.
  • The Shining One's Divine shield bonus is based on Invocations skill.

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: 

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 0.17, 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.

References

  1. ↑ makeitem.cc:806 (0.25.0)
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