Shield (stat)

Version 0.31: This article may not be up to date for the latest stable release of Crawl.

This page is about the Shield stat. For shields in general, see Shields. For the player skill, see Shields (skill).

SH is one of your three physical defenses, along with AC and EV. It allows you to completely negate physical attacks (both melee and ranged) and some magical attacks. Unlike AC and EV, you have no innate SH score. SH gained from wearing a physical shield is governed by the Shields skill; magical shields are unaffected by that skill.

Sources

The following items/abilities can increase your SH:

• Wearing a shield; bucklers, kite shields, and tower shields, in ascending order of effectiveness and cumbrousness
• Wearing an amulet of reflection, Brooch of Shielding, or ring of the Octopus King
• Having the Large Bone Plates mutation
• Using The Shining One's Divine Shield
• Qazlal's Storm Shield passive

Blocking

You can block melee attacks (inc. reaching attacks) and non-penetrating "projectiles" - these include ranged weapons and certain spells like Iron Shot or Poison Arrow.

What can't be blocked by SH:

• Penetrating attacks: Javelins, Bolt spells, Starburst...
• Almost everything with perfect accuracy: Magic Dart, Smiting, Chain Lightning, Explosions (Fireball, Damnation), Shatter...

(Orb of Destruction is the only spell that ignores EV but can be blocked)

• Enchantments: Agony, Pain, Confuse, everything that checks willpower

Max Blocks

Each type of shield (or lack thereof) can only block a certain number of attacks per player turn:

Shield type	Max Blocks
None	1
Buckler	2
Kite shield	3
Tower shield	4

Calculation

If you are wielding a physical shield, its SH is determined as follows:

• Your Base SH is determined by type of shield. 3 for bucklers, 8 for kite shields, 13 for tower shields.
• Add Skill Bonus of (base_SH/40 + 0.19) * skill.
• Add Stat Bonus of DEX * 38 * (base_SH + 13) / 5200.
• Add Enchantment value. +1 enchantment = +1 SH.
• Add 0.82 SH.

All other sources of SH (Qazlal shield, amulet of reflection...) are flat bonuses, and are added on top of the physical shield bonus. The final value is rounded to the nearest integer and displayed as the player's SH value.

If you are paralysed, petrified, or if dexterity is 0, then SH is set to 0 regardless of any other factors.

To-hit vs SH

The game compares the attacker's "pierce value" to the defender's "block value".

The attacker's pierce value is dependent on their to-hit (accuracy) and the type of attack:

• Melee attack: 1d(15 + to_hit/2)
• Ranged attack: 1d(1.3×to_hit)

The defender's blocking value is equal to:

• All attacks: 2d(4×SH)/6 - 1
• Divide by 3 against melee attacks from invisible opponents.

If the blocking value is greater or equal than the attacker's pierce value, and you haven't exceeded the max block count, the attack is blocked.

Strategy

Generally, SH is less effective per point than EV.

• In almost all cases, +1 EV is a better defense than +1 SH. See below for the formulas.
• There is no limit to the amount of attacks you can dodge. There is a limit to the attacks you can block in 1 turn.
• EV defends against penetrating attacks, while SH doesn't.

However, shields give high amounts of SH. Wearing a kite shield instantly brings you from 0 to >8 SH, while gaining 8 EV takes a lot of effort. A shield will almost certainly give more SH than the EV you lose by wearing it. Also, blocking is unaffected by armour encumbrance.

The main costs of wearing a shield are the inability to wield two-handed weapons, and the shield penalties (which can be reduced and eventually removed with Shields skill).

References

1 EV vs 1 SH

In melee, enemies have a to-hit of 1.5 * HD + 18 unless they have the fighter flag. For melee attacks:

• EV dodges if 2d(2EV - 1) / 2 > 1d(to_hit + 1) - 1 .
• SH blocks if 2d(4SH - 1) / 6 > 1d(15 + to_hit/2).

The highest HD of any enemy in the game is 30, so for sake of example, set to-hit = (1.5 * 30 + 18) = 63. Now, let's say you had 30 EV and 30 SH.

• 30 EV: 2d(59) / 2 > 1d(64) - 1; the chance of dodging is 46.48%.
• 30 SH: 2d(119) / 6 > 1d(46.5); the chance of blocking is 39.39%.

In extreme cases, if you have very high EV, 1 SH could be stronger than 1 EV - but only for melee attacks. If an enemy has a to-hit of 36:

• 60 EV, 20 SH:
  • Dodge if 2d(119) / 2 > 1d(35) - 1; the chance of dodging is 94.36%.
  • Block if 2d(79) / 6 > 1d(33); the chance of blocking is 36.12%.
  • Chance to either block or dodge is 96.40%.
• 50 EV, 30 SH:
  • Dodge if 2d(99) / 2 > 1d(35) - 1; the chance of dodging is 91.85%.
  • Block if 2d(119) / 6 > 1d(33); the chance of blocking is 56.11%.
  • Chance to either block or dodge is 96.42%.

In this case, +10 SH is theoretically better than +10 EV. However, you can only block so many attacks per turn, so you should prefer the EV over the same amount of SH.

For ranged attacks, 1 EV is objectively better than 1 SH in all cases.