Using cover

Using Cover or Terrain to One’s Advantage in Melee   The most common situation where terrain provides an advantage to one combatant over another is fighting an opponent who is downhill.   Another situation is fighting with partial cover from a short wall or simple barricade.   Most castle engineers design curved staircases to favor defenders at higher levels against invaders from below.   Rather than get into the minutiae of every specific situation, if one side in a melee fight has a terrain advantage over the other person, the disadvantaged person takes a +1 penalty on all attack rolls.       Using Cover Against Normal Ranged Attacks   Hard cover is cover is that can effectively stop a projectile, usually stone or wood. The more of a target’s body is covered, the harder he is to shoot at.   Roughly 50% cover translates to a +1 difficulty to hit.   Roughly 75% cover translates to +2 to hit.   Near total coverage like an arrow slit translates to +3 difficulty to hit with ranged attacks.     Soft cover impedes line of sight but does impede projectiles.   Mundane smoke or magical mist typically creates a +1 difficulty to hit with ranged projectiles unless the target is practically invisible the in which case they are +2 difficulty to hit.   Passive defense from shields can stack with soft cover but not with hard cover unless you are stacking shields to manufacture hard cover in which case normal shield rules do not apply.       Using Cover Against Area of Effect Attacks   Partial cover is better than nothing when facing a magical fireball or blast of dragon's breath. Partial cover only matters if the cover is strong enough to not immediately crumble under the defense.   50% cover reduces area of effect damage by two successes.   75% cover reduces area of effect damage by three successes.   Hiding behind an arrow slit or something similar reduces area of effect damage by four successes.