Combat
Guard
Guarding cuts incoming foe damage with armor and talent mitigation. Unguarded swings deal the full attack.
While you are Guarding, incoming foe damage is:
damage = max(1, bossAttack − floor(armor × 0.5) − floor(bossAttack × guardMitigationPct / 100))guardMitigationPct comes from talents. Unguarded swings deal max(1, bossAttack).
Guard is the fight-bar brace, not the overnight stance. Overnight Guard is the safe no-income stance. In a fight, Guard is the button that spends a GCD to mitigate the next foe swing.
Rated PvP also gives a Guard opener shield of 5 absorb per level. See PvP stance.