Block is a defensive mechanic that grants a chance to reduce the damage taken from hits.
Whenever you take a hit, your Block Chance is rolled to determine if you block the hit. On a successful block, a percentage of the damage is mitigated.
This percentage depends on how much Block Effectiveness you have, and the level of the area you are in. The percentage cannot exceed 85%.
Where "a" is the zone’s area level and "x" is Block Effectiveness.
You can block all hit (including from spells), but not damage over time effects. Blocking a hit counts as being hit.