Can two mages cast Wall of Fire in the same place?

Question

I've been playing D&D for a long time but I've never encountered this situation until now. If a party has a wizard and a sorceress who both know Wall of Fire, can they cast it in the same place? Say most of the enemies are standing in a big conga line and it's clearly one of the best spells to take them out. The mages happen to come one after the other in the turn order.

The description of Wall of Fire says:

When the wall appears, each creature within its area must make a Dexterity saving throw. On a failed save, a creature takes 5d8 fire damage, or half as much damage on a successful save.

One side of the wall, selected by you when you cast this spell, deals 5d8 fire damage to each creature that ends its turn within 10 feet of that side or inside the wall. A creature takes the same damage when it enters the wall for the first time on a turn or ends its turn there. The other side of the wall deals no damage.

Do the enemies standing in the area of effect take damage from each of the spells when they are cast? If they end their turn in the double fire wall, do they take 5d8 damage from each caster? For instant spells like Acid Splash it makes sense to me that the damage is applied with each cast, even if it is the same type. But if it's a continuous area of effect like Cloud of Daggers (PHB, p. 222), do the damages stack?

Answer 1

Yes, but they don't stack.

PHB 206:

The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect—such as the highest bonus—from those castings applies while their durations overlap.

For your specific case, having two Walls of Fire in the same space does not double the damage. However, if it was a Wall of Fire and a Cloud of Daggers, those effects would overlap and targets in the area would take damage from both.

To answer the title question, nothing prevents the second Wall of Fire from being cast on top of the first, but it wouldn't add extra damage.

Answer 2

Since the spells don't stack, a more efficient tactic than overlapping the walls would be to place the two walls parallel to each other and 11 feet apart, with the fire-sides facing inward towards the other wall.

By doing so, you've now got your opponents trapped in a kill zone. If they exit the hot size of one wall, they immediately enter the hot side of the other wall, forcing a new save.

Answer 3

Arguably, per PHB page 205 the wall of fires will not stack, although the following sentence about Combining magical effects gives an example about beneficial spells, not damage spells.

For example, if two clerics cast bless on the same target, that character gains the spell's benefit only once; he or she doesn't get to roll two bonus dice.

I think this is too vague to say whether or not the initial damage of the 2nd instance of wall of fire is or isn't applied. However, if the caster of the first wall of fire ends concentration:

From the Sage Advice compendium:

Can a spellcaster dismiss a spell after casting it? You can’t normally dismiss a spell that you cast unless (a) its description says you can or (b) it requires concentration and you decide to end your concentration on it. Otherwise, a spell’s magic is unleashed on the environment, and if you want to end it, you need to cast dispel magic on it.

Also on page 203 of PHB:

You can end concentration at any time (no action required).

In either case, I would rule that the initial damage of both walls of fire applies, but the "additional damage at end of turn" is applied once.

However, if the two casters able to cast wall of fire coordinate their efforts, the first could end concentration right before the 2nd casting of the spell, so you could definitely get 2x applications of the initial damage, along with the damage to creatures ending their turn on that side of the wall.

However, you could easily fit a few walls of fire within the same 5' x 5' square if you lined them up properly, so if you had each wall pointing in opposite directions, you could get 2x initial burst (since the wall of fires would then not be in exactly the same location) and also cover both directions from the origin points, since the origin points are slightly different.

For purposes of combining magical effects, I tend to think that whether you are fully in one fire or the other, or half in each, the damage will still be the 5d8 at the end of your turn but your DM ruling may vary.

But certain vagaries can definitely be worked around via concentration!

Answer 4

Really, it's up to the DM but in my experience, area effect spells of the same type do not stack, so victims wouldn't take double damage. However, if I was DM, I'd probably insist that victims would have to make a saving throw for each instance of the spell, failing any would result in full damage.

Answer 5

I wanted to add that if you cast the walls parallel to each other, you could face the heat wave effects inward, meaning that each wall projected its heat wave towards the other wall. In that case, standing inside of one wall of fire would proc the contact damage from that wall as well as the heat wave damage from the second wall.

As a thought experiment, assume there are actually three walls of fire: A,B,C Direction of heat wave: A-, -B, -C

If you arranged your walls as ABC, and a creature stood inside of wall B, they would take contact damage from B, plus they would take additional heat wave damage from both A and C.

Answer 6

As per p206 of the PHB, they don't stack. They may have to make two saving throws if you land two on a person but they would only take 5d8 damage even if they failed both saving throws.

The only benefit to having two walls in the same row would be to have them pointing in opposite directions. However, it would be better to have the walls back to back rather than in the same row. That way you add one more 5' row to the damage and you can force saves on more people (unless they are lined up in one row).

Now, if you have the two walls facing each other with a 5' gap between the hot zones and combine that with a rolling boulder trap. You can give the targets a choice between a rock and a hot place.