Spells: Line of Effect vs Line of Sight

Post date: Mar 03, 2017 11:2:9 PM

Spell targeting can be a confusing topic, so here we go over the requirements for spell targeting.

Line of Effect: To target something, you must have a clear path to it, so it can’t be behind total cover. If you place an area of effect at a point that you can’t see and an obstruction, such as a wall, is between you and that point, the point of origin comes into being on the near side of that obstruction. 

• • Note that a closed glass window is considered total cover, even though you can see through it. Same is true of a Wall of Force.

  • Spells that require you to choose targets require Line of Effect, unless the spell description specifically says otherwise.

  • Example of spells that ignore total cover: Sacred Flame, Detect Magic, Message

  • Known Location: If you don't know the specific location the target is on, you may make a guess and let the GM know of the spell effects. If you guess correctly and there is Line of Effect, then the GM will apply the results (you may not know whether you targeted a creature or not).

  • No Stealth action: You know the specific location of any creature who is not using Stealth to conceal themselves.

    • Successful Stealth action: The hidden condition (attainable by using Stealth) means you don't know where the target is, and thus must guess which square to target.

      • Not visible: If you cannot see the target, but could potentially hear the target, you may make a Perception check with disadvantage (house rule)

        • If you succeed on the 1st roll, you know there is a target in the area, but do not know his specific location.

        • If you succeed at both rolls, you can pinpoint which square the target is located on.

      • Light obscurement (such as dim light, darkness with darkvision, patchy fog, or moderate foliage): Gives disadvantage on Perception checks relying on sight.

Line of Sight: Many spells detail in the spell description that you must see the target.

• • Line of Effect: Spells requiring Line of Sight must still meet Line of Effect, unless the spell description says otherwise.

  • Known Location: These spells may not be targeted against creatures you cannot see, even if you know where the target is.

  • Obscurement & Invisibility: Heavily obscured (such as darkness, heavy fog, or dense foliage) and Invisibility are common ways that block you from targeting spells requiring you to see the target.

  • Examples of spell that require you to see the target: Control Flames, Create Bonfire, Frostbite, Lightning Lure, Mold Earth. Poison Spray, Sacred Flame, Shape Water, Vicious Mockery

  • Examples of spell that don't require you to see the target: Acid Splash, Booming Blade, Chill Touch, Eldritch Blast, Fire Bolt, Gust, Magic Stone, Produce Flame, Ray of Frost, Thorn Whip.

    • Note that spells needing attack rolls still require you to have disadvantage if you cannot see your target.

  • Our spell summary sheet has a column for which spells require you to see the target.

Summary Examples:

• • Sacred Flame against a target you can see on the other side of a window or wall of force (ie total cover), works just fine. 

  • Frostbite against a foe who is crashing through dense foliage that blocks you from seeing the target, even though you know which square they are in, you cannot target this foe.

  • Chill touch against a unseen foe in a darkness spell, you can guess which square he is in and make a ranged spell attack with disadvantage. The GM applies the spell effect if you guessed correct and hit (yopu may well not know if you succeeded).