I have a mechanics question relating to the Web spell. My understanding is that the webs created by this spell fill a 20' cube and that they collapse if they are not anchored between two solid masses (e.g., walls) or are layered across a floor, wall, or ceiling. Recently I tried to cast Web into a dungeon corridor that was 15' wide. The DM stated that I could not do so since the AoE marker in Roll20 (a 20' square) was too large for the space. However, I see nothing in the spell's description to suggest that the space has to be 20' wide and assume the webbing would fill the available space as long as the constraints above are met, potentially increasing in height and length if the available width is less than 20'.
Has anyone else dealt with this issue or can point me to an "authoritative" (e.g., Sage Advice, JC Tweet) interpretation? Thanks.
The DM states you must find a 20x20 space? Then he needs to adjust the room/hall sizes. To say you can only cast in a 20x20 space sounds like a bad DM. The marker needs to be adjusted.
[...] However, I see nothing in the spell's description to suggest that the space has to be 20' wide and assume the webbing would fill the available space as long as the constraints above are met, potentially increasing in height and length if the available width is less than 20'.
I'd say you're right, based on the rules. For example, for the 2024 ones:
An area of effect has a point of origin, a location from which the effect’s energy erupts. The rules for each shape specify how to position its point of origin. If all straight lines extending from the point of origin to a location in the area of effect are blocked, that location isn’t included in the area of effect. To block a line, an obstruction must provide Total Cover. See also “Cover.”
So depending on the point of origin, the Area of Effect can be blocked, but the spell can still be cast. It's similar for the 2014 rules:
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.
Also, this answer is from the 2014 SAC:
Can a spell such as fireball go past its 20-foot radius if the point of origin is set in an enclosed space that’s less than 40 feet across?
The fire of the fireball spell can spread around corners, but it’s limited by the spell’s 20-foot radius. It doesn’t extend farther than 20 feet from the point of origin no matter where it is cast.
Just note the 2024 Fireball doesn't spread around corners, but I think the rest of the answer is still useful.
I agree it should have been allowed. There are some powers that say something like, if there’s not enough space this fails, like a rune knight when they turn large, for example. But this has no language like that. In this case, it’s a little bit like you are nerfing yourself. You are using a spell, deliberately knowing you’re shorting yourself 5’ of area. The slot was still expended same as if you’d been able to cover 20’.
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I have a mechanics question relating to the Web spell. My understanding is that the webs created by this spell fill a 20' cube and that they collapse if they are not anchored between two solid masses (e.g., walls) or are layered across a floor, wall, or ceiling. Recently I tried to cast Web into a dungeon corridor that was 15' wide. The DM stated that I could not do so since the AoE marker in Roll20 (a 20' square) was too large for the space. However, I see nothing in the spell's description to suggest that the space has to be 20' wide and assume the webbing would fill the available space as long as the constraints above are met, potentially increasing in height and length if the available width is less than 20'.
Has anyone else dealt with this issue or can point me to an "authoritative" (e.g., Sage Advice, JC Tweet) interpretation? Thanks.
The DM states you must find a 20x20 space? Then he needs to adjust the room/hall sizes. To say you can only cast in a 20x20 space sounds like a bad DM. The marker needs to be adjusted.
I'd say you're right, based on the rules. For example, for the 2024 ones:
So depending on the point of origin, the Area of Effect can be blocked, but the spell can still be cast. It's similar for the 2014 rules:
Also, this answer is from the 2014 SAC:
Just note the 2024 Fireball doesn't spread around corners, but I think the rest of the answer is still useful.
I agree it should have been allowed. There are some powers that say something like, if there’s not enough space this fails, like a rune knight when they turn large, for example. But this has no language like that.
In this case, it’s a little bit like you are nerfing yourself. You are using a spell, deliberately knowing you’re shorting yourself 5’ of area. The slot was still expended same as if you’d been able to cover 20’.