The most common type of Block is Passive Block, a chance-based stat that's rolled on a per-Hit basis. Unlike Evasion, Passive Block is entirely random, and upon rolling successfully, an incoming Strike or Projectile will have all of its Damage prevented. When Passive Block chance is rolled unsuccessfully, the Hit is not Blocked, and no Damage is prevented.
Base Block Chance
The base chance to Block is typically derived from an equipped Shield, but can also come from other items such as the
Barrier Quarterstaff. For example
Mahuxotl's Machination has a base Block chance of 25%.
When a Shield has an 'increased Block chance' modifier present, this a local modifier that directly scales the base Block chance provided by the Shield. For example
The Surrender with a modifier roll of '50% increased Block chance' would bring the base Block provided by this Shield from 26% up to 39% (26 * 1.5)
You can also find rarer modifiers that add directly to the base Block chance, such as the one on
Legionstride. These modifiers are recognisable from their terminology, adding to Block chance rather than increasing it.
Global Block Chance
Global modifiers that provide 'increased Block chance' do not add their percentage to the base chance obtained from Shields or elsewhere. Instead, these modifiers are multipliers to the base Block chance. Taking the example from above,
The Surrender providing 39% base Block chance would be improved to 44% if the player allocated the
Vigilance Passive Skill Tree Notable (39 * 1.12).
Maximum Block Chance
The default maximum Block chance is 75%. This can be improved by rare modifiers such as the one on
The Anvil.
Maximum Block chance is hard-capped at 90%.