When a spell has no defined shape (i.e. Cone, Line, Sphere, etc.) is it up to the DM/group to decide its shape or is there a commonly held RAI interpretation?

e.g. Spirit Guardians

[Spirits] flit around you to a distance of 15 feet for the duration.

Is this implied to be a 15' radius sphere suggesting that the spirits can fly? Perhaps a cylinder of the same radius with a height equal to that of the caster's, or maybe with a height defined by the vertical reach of the spirits conjured?


Spells that have no "defined shape" have the area they affect specified in the spell description. And, remember the general rule that spells do what they say they do.

Spirit Guardians has the following Range property:

Range: Self (15-foot radius)

So it explicitly has a radius and could thus be either a cylinder or a sphere. It actually probably doesn't matter which one, because of how the spell is described.

First of all, don't get too hung up on the fact that the spell "calls forth spirits"; they aren't creatures and don't have any characteristics, so worrying about whether they fly or not or how far they can reach is pointless. The spirits are a special effect of the spell; that is, a description attached to the spell that, while interesting and evocative, doesn't have a game-mechanical effect.

The spell halves the speed of creatures in the area, and causes them damage on their turns. The 'area' is the space that's within 15 feet of the caster. That's it. For making rulings about whether someone nearby is or isn't affected, you don't need to think about whether spirits fly or not; just decide if the creature in question is within 15 feet of the caster.

Most of the time, the "sphere or cylinder" distinction won't make a difference here; it only matters if characters are flying and occupy a position that's close to 15' in the air and also close to 15' horizontally distant from the caster. But it doesn't break anything for the DM to just say that's close enough to be affected by the spell.


Based on the information you have provided, I can almost assure you that it represents a sphere around the caster. In any case, there is no logic backing that spirits can fly over 15 feet over the character but can't fly over 15 feet horizontally away from the caster.

I would recommend revisiting the Monster Manual for a hovering height for similar creatures, but since they flit I would guess they don't fly too high.

Anyways, I would recommend to follow Rule #1,

If in doubt, make it up.

Or something like that. Restricting them to a cube would lead to more complicated questions such as is the cube oriented to the caster's position? when considering the edges of the cube.

Stick to your answer and let the story flow, 5E allows you to create your own set of rules, anyways.

  • 2
    \$\begingroup\$ Spirit guardians doesn't summon creatures, so nothing in the Monster Manual is relevant to interpreting the spell effects. \$\endgroup\$ – Marq Feb 12 '16 at 12:27

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