How much cover does Wall of Stone give against a dragon's breath weapon if arrow slits are included in the wall?

Question

I am currently a sorcerer in the Rise of Tiamat campaign (plenty of dragons to come I assume). I am obviously asking this as a player; I am not a DM and never go through the DMG/Monster Manual (so this could be covered in those books).

Say I cast the wall of stone spell, during or prior to combat against a white dragon, and this wall was designed with arrow slits in it for ranged attacks and cover.

How much cover would we get against the dragon's breath weapon - three-quarters cover or full cover? Or would it work like fireball, which spreads around corners?

Related: Can I ready an action to block a breath weapon with Wall of Stone? — Purple Monkey, Jul 24 '18 at 04:34

Gandalfmeansme · Answer 1 · 2018-07-24T12:43:34.503

12

Probably 3 Quarters Cover

Consider the rules for three quarters cover, given in the Players Handbook (p.196, bold added for emphasis)

A target with three-quarters cover has a +5 bonus to AC and Dexterity saving throws. A target has three- quarters cover if about three-quarters of it is covered by an obstacle. The obstacle might be a portcullis, an arrow slit, or a thick tree trunk.

If you create arrow slits in the wall, and are using them for ranged attacks, you have three Quarters Cover. If you made the wall with arrow slits, but no straight line exists from your enemy's space to your space that goes through the arrow slit, you will have full cover via the wall (rules for cover that support this can be found on the DMG, p. 251). Note that dragons' breath weapons don't explicitly go around corners, so full cover would be granted if you satisfy the requirements described above.

Three major things to consider:

The spell Wall Of Stone does not explicitly state that you can create arrow slits in it. And while it does state "You can crudely shape the wall to create crenellations, battlements, and so on," it also requires that each 10' by 10' panel of the wall must be contiguous with at least one other panel. You may need to consult with your DM as to whether you can create arrow slits in such a wall, and how.
Not all dragon breath weapons give Dexterity saving throws. Some give Constitution saving throws. As three quarters cover only gives bonuses to Dexterity saving throws, keep in mind that your wall may not give much protection from a breath weapon if it is full of small gaps. (I won't say which kind of save a White Dragon's breath weapon gives. You specified you haven't read the DMG or Monster Manual, and I assume that was by choice).
Dragons can fly. If you hope to give yourself full cover from the dragon, you may need to completely enclose yourself within this wall.

edited Jul 24 '18 at 12:43

answered Jul 24 '18 at 04:48

Gandalfmeansme

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Example if I made the wall 40 wide and 30 high, say the arrow slit is made 10ft from the right end of the wall, I take my range attack then use my movement to move 15ft to the left behind the wall. This I would assume would be "Total Cover"?
1. In the "wall of stone" description it states, You can crudely shape the wall to create crenulations, battlements, and so on etc. - surely an arrow slit would be part of this.
2. Okay noted, the main point I want to clear up is completely avoiding the breath so no save is needed.
3. I am more or less meaning a front on direct attack. but TY
– Josh Robinson Jul 24 '18 at 05:09
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1.) It would if there is now no line from anywhere in the dragon's space to anywhere in your space through a slit. If there is, you have 3/4 cover. Whether or not that happens largely depends on where the dragon is relative to you/your wall. As for the arrow slits, battlements and crenulations are crudely shapeable: an arrow slit may be more refined. And more importantly, "each panel must be contiguous with at least one other panel." An arrow slit may violate this rule, depending on how you create it. 2.) I hope I've cleared that up. 3.) The dragon's position and movement will matter there. – Gandalfmeansme Jul 24 '18 at 05:16
okay great that does clear that up, I was mainly clarifying the cone breathe doesn't have the same affect as the fireballs spread and total cover is possible. 2. yes thank you 3. yes of course and of course it would be very situational but definitely a great option given the area wall of stone can cover.

Thanks mate

Josh Robinson

Jul 24 '18 at 05:19

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@Gandalfmeansme: Wall of Stone does say "You can crudely shape the wall to create crenellations, battlements, and so on." I assume that's where OP got the arrow slit part from. – V2Blast Jul 24 '18 at 05:37

1

To be fair, crenelations probably count as 3/4 cover anyway, if a large tree does. – Darth Pseudonym Jul 24 '18 at 18:57

But you can fly over a crenelation. If you constructed the wall of stones to surround you completely (above and on the sides), then arrow slits become a rather different part of the equation. – Gandalfmeansme Jul 24 '18 at 19:07

ravery · Accepted Answer · 2018-07-24T17:33:09.847

Let's start with your incorrect premise: an Area of Effect does not go around corners (unless specified by the effect). There must be a clear path to the point of origin for the effect, and then a clear path from the point of origin to the affected creature. This might seem like going around corners but is actually two straight lines. [See Area of Effect and Cover, DMG p251.]

In the case of dragon's breath, the point of origin is the dragon, with the Area of Effect being a ray or cone. Thus, there must be a clear line from the dragon to the target.

Arrow slits provide 3/4 cover [DMG p251]. Dragon's breath would come through the slits. If there are places on the wall where you could stand away from the arrow slits, those spots would have total cover (see below diagram for a cone AoE).

Thus, if you are standing at the arrow slit casting spells or shooting at the dragon when it uses its breath weapon, you would need to make the required save.

By RAW, 3/4 cover gives +5 to AC and Dex saving throws [PHB p196]; however, a DM may house rule advantage instead of +5 on the save if a square with total cover is next to you.

Comments are not for extended discussion; this conversation has been moved to chat. — mxyzplk, Jul 24 '18 at 18:45
Thank you for editing and putting the time into the diagram, that is perfect. — Josh Robinson, Jul 25 '18 at 02:03
I think it should be noted that this means that (RAW) while standing in front of the slit you get no benefit whatsoever against the breath of a white dragon (the example in the Q), because it asks for a Con save, not Dex. — Szega, Mar 26 '20 at 07:47

How much cover does Wall of Stone give against a dragon's breath weapon if arrow slits are included in the wall?

2 Answers2

Probably 3 Quarters Cover

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