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According to answers to this question wall of force follows rules for area spells (PHB, 204)

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

Now, a hypothetical situation. Mage is trying to cast wall of force in a sphere around a creature. There are several possible variants and related questions:

Variant A

Sphere is placed in such a way that wall intersects creature. According to description of wall of force it causes creature to move to one side of the wall, caster's choice. Does it happen before or after the area of the spell's effect is calculated? I.e. does such a moved creature leave a silhouette-shaped hole in the wall or not?

Variant B

Sphere is placed in a way that creature is within it. Point of origin is as close to creature as possible. Obviously some straight lines from point of origin to a some locations upon the sphere are blocked by said creature. For some of those locations the creature is likely to provide total cover. Does it mean that wall of force would have holes in that case?

Variant C

Wall of force in a 5-foot diameter sphere option cast next to 6-foot tall creature. What happens with the creature? Is it forced to kneel or somehow else fit into the sphere, or is it just moved, but still standing as it was standing, with his head and shoulders sticking through a hole in the wall of force sphere? What if sphere is smaller? I.e. is it possible to use wall of force as a trap, encasing only parts of creature and leaving the rest sticking outside?

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  • \$\begingroup\$ Welcome to RPG.SE! Take the tour if you haven't already, and check out the help center for more guidance. \$\endgroup\$
    – V2Blast
    Commented Sep 25, 2019 at 5:14
  • \$\begingroup\$ I changed your "5 foot radius" to "5 foot diameter" in your last example because it seems to be what you meant. A 5 ft radius sphere (being 10 feet tall) would easily hold a 6 ft creature. If this isn't what you meant feel free to revert my edit. \$\endgroup\$ Commented Sep 25, 2019 at 13:13

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In variant A and B, a creature doesn't cast a "shadow" in a spell's area of effect. As you said:

To block one of these imaginary lines, an obstruction must provide total cover

Creatures do not provide total cover; they provide half cover, as described in the Cover rules in the Player's Handbook (p.196):

A target has half cover if an obstacle blocks at least half of its body. The obstacle might be a low wall, a large piece of furniture, a narrow tree trunk, or a creature, whether that creature is an enemy or a friend.

So creatures don't block spell effects. You can't hide behind the fighter to avoid a circle of death, and a creature doesn't create a looney-tunes hole in a wall of force.

Cover is handled on a square-by-square basis, not an inch-by-inch or foot-by-foot basis. This is discussed in full in the Dungeon Master's Guide, p.251, with illustrations on p.250 and 251.

Variant C is effectively a duplicate of this question from a couple years ago, and answered thoroughly there. Personally, I would rule that when the caster selects which side of the wall to force a creature to, they can't pick a side that's too small for the creature to squeeze into, so you could use this trick to constrain a creature and give them disadvantage, but not actually harm them. It is of course possible to imagine a situation where both sides of the wall are too small (like if the creature is already squeezing and you then drop the wall right in the middle of the passage), so that doesn't make for an entirely satisfactory ruling -- but on the other hand, that's a really odd corner case that's unlikely to happen in actual play, and can probably be handled on the fly when and if it actually comes up.

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  • \$\begingroup\$ What about situations like a Stone Wall bisecting a square. A creature on the near side would have no cover, one on the far side would have total cover. So objects smaller than 5-foot squares make difference in cover. I think the reason creatures only give half cover is that they normally do not fill the entire 5-foot cube and they move around. But if you are looking at exactly the body shadow of the creature, would not anything entirely behind it have full cover? \$\endgroup\$ Commented Feb 1, 2022 at 8:52
  • \$\begingroup\$ Not sure what you're getting at here. If you have a wall that bisects a square, the wall is clearly larger than a five foot square. To provide total cover, the wall must be tall enough to fully block squares behind it. If it's a chest high wall, then it provides only partial cover to squares behind and doesn't stop the spell from reaching them. In any case that's what I meant about cover being handled by square, not by inch. You don't get to call out a specific square inch and ask if it has total cover; that isn't how the rules work. \$\endgroup\$ Commented Feb 1, 2022 at 12:46

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