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The spell description of wall of force is silent on the question of whether spell effects can pass through the wall. The semi-relevant part of the description states:

Nothing can physically pass through the wall. It is immune to all damage and can't be dispelled by dispel magic. A disintegrate spell destroys the wall instantly, however. The wall also extends into the Ethereal Plane, blocking ethereal travel through the wall.

How are folks ruling on the question of spells passing through the wall (in both directions)? If the answer is that spells cannot pass through the wall, do you rule that it also blocks line of effect (so that you can't target a spell on the other side)?

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Mike Mearls rules Wall of Force does block spells, including lines of effect

Quoting Mike Mearls on Twitter:

Aug 28Jim Miller ‏@pokereleran@mikemearls Is there a line of effect in D&D and does Wall of Force block it?

Mike Mearls – ‏@mikemearls@pokereleran in general, a barrier that stops physical objects stops spells

In terms of this being a 'Word of God' answer, I'm aware the mantle of authority has passed from Mike Mearls to Jeremy Crawford. But this is still a ruling from someone who knows the game supremely well.

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    \$\begingroup\$ Does "stops spells" apply only to spells that must pass through (like ray of frost) and not to spells that can be targeted on the other side of the wall (like sleet storm)? \$\endgroup\$ – PurpleVermont Apr 18 '15 at 21:27
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    \$\begingroup\$ @PurpleVermont it would be both. you need a "clear path" to the origin point of the spell \$\endgroup\$ – wax eagle Apr 19 '15 at 1:49
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    \$\begingroup\$ I couldn't believe the logic therein, so I checked out the citation linked, and Mearls had a followup to his quoted response, Sep 30:‏ "would block physical effect of spell but not mess with targeting that needs sight #wotcstaff" \$\endgroup\$ – pulverize Mar 29 '17 at 0:10
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    \$\begingroup\$ Jeremy Crawford talked at length about spell targeting in a WotC podcast on Jan 19, if you'd like far superior evidence to support this answer. \$\endgroup\$ – Derek Stucki Mar 29 '17 at 17:51
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    \$\begingroup\$ -1 I know you mention this in your answer, but I find that an answer based only on a developer is a poor answer in general. And when the developer isn't even the one able to make official rulings even less so. So I find this answer does not really help clarify the issue at all. If you actually reference the text and provide some evidence there for this viewpoint then it would be much improved. \$\endgroup\$ – Rubiksmoose Sep 26 '18 at 18:07
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A wall of force blocks magic by granting total cover.

Although this is an old question, I discovered a relevant ruling while researching another question, and would like to add it here for completeness.

D&D 5e designer Jeremy Crawford, whose rulings are considered official, confirms in a tweet that wall of force provides total cover:

Q: could a wizard make a sphere around a creature using wall of force and then chill touch to damage them through the wall?

Crawford: Unless a spell says otherwise, you can't target someone behind total cover (PH, 204)

Also here, in specific reference to wall of force:

Q: Wall of Force is invisible...so it doesn't provide cover does it?

Crawford: Cover is a physical obstruction, not necessarily a visual one.

The reason wall of force blocks spells is that it, as an obstacle, it provides total cover to anyone fully behind it as per PHB p.196:

A target has total cover if it is completely concealed by an obstacle.

Crawford's ruling confirms that "concealed" here is a synonym for "covered", not "invisible" as it meant in earlier editions of the game. And, as per PHB p.204, this prevents a caster from targeting you:

To target something, you must have a clear path to it, so it can't be behind total cover.

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  • \$\begingroup\$ There are a lot of cases that "total cover" doesn't handle. What about misty stepping in or out? What about line 0f effect, so that you might target a fireball inside? \$\endgroup\$ – PurpleVermont Sep 24 '18 at 16:52
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    \$\begingroup\$ Misty step is a teleport, which is covered by Does the Wall of Force spell block teleportation? The cover rules already handle the case of area-of-effect effects and total cover ("some spells can reach such a target by including it in an area of effect"). \$\endgroup\$ – Quadratic Wizard Sep 24 '18 at 18:02
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    \$\begingroup\$ @PurpleVermont Misty Step is also a self targeting spell. See the podcast on Jan 19, 2017 for how targeting is supposed to work from JC. And QuadWiz you could add that to your list of evidence. \$\endgroup\$ – Slagmoth Sep 24 '18 at 19:23
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    \$\begingroup\$ @PurpleVermont Wouldn't any space beyond the wall of force all be considered behind "Total Cover", meaning you can't target the square due to cover rules? Fireball also has a physical projection (the flame streak), which couldn't pass through the wall. \$\endgroup\$ – Play Patrice Sep 25 '18 at 2:25
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    \$\begingroup\$ Note: Crawford's tweets are no longer official. \$\endgroup\$ – V2Blast Jun 25 at 8:43
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Nothing being able to pass through the wall makes it count as total cover, and that makes targets on the other side of it invalid spell targets. From "Targets" in the PHB's Spellcasting chapter, page 204:

To target something, you must have a clear path to it, so it can't be behind total cover.

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    \$\begingroup\$ "Total cover" in 5e is determined by line of sight, so how does an invisible wall block that? \$\endgroup\$ – Shalvenay Apr 18 '15 at 3:23
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    \$\begingroup\$ @Shalvenay All degrees of cover are about blocking… except for the wording of total cover. Except that they are introduced as three degrees of the same thing, so it's pretty clear that total cover is about being totally blocked, visibility through an exceptional invisible blocking cover notwithstanding. Otherwise, you could shoot arrows with impunity through a glass wall three feet thick; reductio ad absurdum then supports the simpler, saner, and more consistent "three degrees" reading. \$\endgroup\$ – SevenSidedDie Apr 18 '15 at 3:30
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    \$\begingroup\$ total cover applies only to targeting; you can shoot arrows at a target on the other side of the glass wall three feet thick, but of course they'll never make it there. \$\endgroup\$ – Shalvenay Apr 18 '15 at 3:42
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    \$\begingroup\$ can we agree that the 5e PHB made a lousy decision when it comes to choosing "concealed" in the definition of total cover? \$\endgroup\$ – Shalvenay Apr 18 '15 at 3:54
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    \$\begingroup\$ This is why 5e is written with smart human interpretation in mind, not for smart human interpreters mistakenly assuming it's written for dumb computers. \$\endgroup\$ – SevenSidedDie Apr 18 '15 at 7:02
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There are three potential interpretations in play here:

  • One interpretation is that visual concealment is necessary for total cover, leaving targets on the other side of a wall of force, or a mundane transparency such as a floor-to-ceiling windowpane for that matter, fully targetable by spells and spell effects, or even mundane attacks (albeit with no guarantee of success).
  • Another interpretation is that even a transparent surface grants total cover, as it is a physical obstacle, albeit one unable to actually conceal a target.
  • The middle-of-the-road path is that spells can be targeted based on line of sight (including through magical and mundane transparent walls and surfaces).
    • Spell effects with physical components (fireballs, rays and such) behave like mundane projectiles and cannot pass through a transparent surface of any sort as a result, or are restricted in how they can pass through them.
    • Spells whose effects are immaterial (such as a mind-altering dominate spell) can freely traverse something transparent.

The applicable RAW is as follows (PHB p. 204):

A Clear Path To the Target

To target something, you must have a clear path to it, so it can't be behind total cover.

and (under Areas of Effect)

A spell's effect expands in straight lines from the point of origin. If no unblocked straight line extends from the point of origin to a location within the area of effect, that location isn't included in the spell's area. To block one of these imaginary lines, an obstruction must provide total cover, as explained in chapter 9.

Going to p. 196 of Chapter 9 of the PHB where total cover is defined:

A target with total cover can't be targeted directly by an attack or a spell, although some spells can reach such a target by including it in an area of effect. A target has total cover if it is completely concealed by an obstacle.

Wall of force (p. 285) does not grant any concealment:

An invisible wall of force springs into existence at a point you choose within range. ...

However, since it is a barrier:

Nothing can physically pass through the wall.

it clearly meets the definition of obstacle, leading us off the end of the RAW, and into RAI territory.

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    \$\begingroup\$ It is possible to have total cover but no concealment. For example, being in the middle of a gelatinous cube. \$\endgroup\$ – Greenstone Walker Apr 18 '15 at 10:55
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    \$\begingroup\$ @GreenstoneWalker Even more simply, and less gross and painful, behind a wall with a closed window in it. \$\endgroup\$ – Slagmoth Sep 24 '18 at 19:39
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The wall of force has a number of different configurations. Some of them may block line of sight but at least one does not.

The spell's description says that the wall can be "free floating or resting on a solid surface."

It also states that it can be formed into a "hemispherical dome."

Assuming that one wants to be able to cast spells on a target trapped inside a wall of force then by RAW the wall can be formed as a hemisphere suspended in mid-air roughly six inches off the ground, which should be sufficient to both trap most targets inside but yet give the caster sufficient line of sight to affect the target inside.

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    \$\begingroup\$ Hemispheres aren't domes. Domes are open on the bottom; hemispheres are not. \$\endgroup\$ – RonLugge Jun 28 '18 at 3:27
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A wall of force can only be destroyed by a disintegrate spell and it extends to the ethereal plane. An exception to this rule is a spell where you target a place/something you can see with finger of death or a similar spell:

You send negative energy coursing through a creature that you can see within range, causing it searing pain. The target must make a Constitution saving throw. It takes 7d8 + 30 necrotic damage on a failed save, or half as much damage on a successful one.

A humanoid killed by this spell rises at the start of your next turn as a zombie that is permanently under your command, following your verbal orders to the best of its ability.

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    \$\begingroup\$ That is not what the spell says: "A disintegrate spell destroys the wall instantly". Disintegrate can destroy the wall but it never says it penetrates the wall such that you could target something inside of WoF while it was still active. That is what the question is asking about. Also, I'm not sure what the ethereal plane has to do with anything honestly. \$\endgroup\$ – Rubiksmoose Sep 26 '18 at 15:58
  • \$\begingroup\$ I'm sorry for the miscommunication and if a spell was to be cast on the ethereal plane it could go through the space where the wall would be unless the wall was in the ethereal plane. \$\endgroup\$ – Demonshpawner Sep 26 '18 at 16:25
  • \$\begingroup\$ Actually, what I am saying is that disintegration cannot pass through the wall regardless of the plane it's on. It can destroy it, but it can't pass through the wall without destroying it and hit something else. \$\endgroup\$ – Rubiksmoose Sep 26 '18 at 16:28
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    \$\begingroup\$ I don't think Finger of Death can pass through Wall of Force. The spell's description starts "You send"... meaning the negative energy has to travel from you to the target that you can see. Just because you can see something doesn't mean you can hit it (see above about glass windows or gelatinous cubes). \$\endgroup\$ – TylerH Sep 26 '18 at 16:42
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    \$\begingroup\$ @Demonshpawner: That is actually not true. Read the other answers above yours. Every spell is by default blocked by WoF because WoF provides cover and you cannot target anything behind full cover. There are a few who can avoid it, but they have to specifically say so. \$\endgroup\$ – Rubiksmoose Sep 26 '18 at 16:54

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