What are the permitted shapes of a Wall of Fire?

Question

The text of the Wall of Fire spell is found on page 285 of my printing of the Fifth Edition Player's Handbook. The following is all the text states regarding how the wall is shaped:

[...] You can make the wall up to 60 feet long, 20 feet high, and 1 foot thick, or a ringed wall up to 20 feet in diameter, 20 feet high, and 1 foot thick.

I believe there are two reasonable readings of this text:

1. The wall is an arbitrary shape whose length does not exceed 60 feet. As a special case, if the shape is a ring, its length is instead the circumference of a circle whose diameter is 20 feet (in other words, treat pi as 3 for the sake of simplicity).
2. The wall has exactly two permitted shapes: a straight line up to 60 feet long, and a circle 20 feet in diameter.

I haven't been able to find any additional clarification from official sources indicating which reading is intended, but I have found plenty of evidence indicating that different people are using both of these interpretations in play, citing indicative but not conclusive evidence outside the spell text. What is the official intended reading for this spell?

Answer 1

It's probably a straight line (or a ring).

There are many wall of- spells in D&D 5e. Regarding shape of the wall, many use this formula:

You can make the wall up to X feet long, Y feet high, and Z feet thick.

Then, some of them go on to define alternative shapes. The following spells follow this formula (those defining an alternate shape are denoted below with a †):

• prismatic wall† (PHB, pg. 267)
• wall of water† (EEPC, pg. 170)
• wall of fire† (PHB, pg. 285)
• wall of light (XGtE, pg. 170)
• wall of sand (EEPC, pg. 170)

Each of these spells lets you make a wall, and three of them define an alternate shape.¹

There is another wall spell, wind wall (PHB, pg. 288), which has a very important feature that is notably absent from these other wall spells:

You can shape the wall in any way you choose so long as it makes one continuous path along the ground

This phrase is entirely unique to wind wall. Wind wall uses the typical formula these other spells use, then it is uniquely defined as being able to make a wall of any shape.

If the intent of the statement:

You can make the wall up to X feet long, Y feet high, and Z feet thick

is to allow you to make a "wall" having any shape, then this unique feature of wind wall is entirely redundant.

There is room for an alternative ruling.

Obviously there is some ambiguity. My argument above requires understanding and comparing wall of fire to five other spells and saying "one of these is not like the others". The trouble with ruling that wall of fire can be any shape is that this ruling says "even though one of these is not like the others, I'm going to rule they're all the same." There's room for this given the ambiguity of what a wall is in this context, but I don't think it is the right ruling given the uniqueness of the description of wind wall.

---

¹ There is another category of wall spells that has you arranging "panels" of some dimension; this category includes: wall of stone, wall of force, and wall of ice. This mechanic of arranging panels is sufficiently different from these other wall spells that I do not think they are relevant for making a ruling on wall of fire.

Answer 2

It can be any shape you want up to the dimensions indicated

RAW ruling does not indicate it is a specific shape so it is not

As described in PHB P7, under the Specific beats general section, Spell rules are specific to each spells and self contained, using other unrelated spells descriptions to try and determine how the wall of fire works is not the right thing to do in my opinion unless you play RAI.

Conclusion: You could actually 'aim' you wall of fire to be any shape and as sinuous as you want to appear on as many creatures as you want.