6

Say a Twilight Domain cleric has Channel Divinity: Twilight Sanctuary and the spirit guardians spell in effect. The cleric then uses the Steps of Night feature to fly up 15-30 feet.

Does the Twilight Sanctuary sphere maintain its 30-ft. radius on the ground, and does the spirit guardians spell maintain its 15-ft. radius on the ground?

V2Blast
  • 49,864
  • 10
  • 220
  • 304
Captronc27
  • 61
  • 2
  • 1
    Welcome to RPG.SE! Take the [tour] if you haven't already, and check out the [help] for more guidance. – V2Blast Mar 07 '22 at 18:38

2 Answers2

6

The centers move with you.

Both features, spirit guardians and Twilight Sanctuary, create spheres centered on you:

Twilight Sanctuary

[...] The sphere is centered on you

Spirit guardians

They flit around you to a distance of 15 feet

If you move, the center of the sphere moves with you. Naturally, this will have the effect of reducing the radius of the effects area on the ground as your distance from the ground increases.

That said, 3d-space rules are somewhat underdefined, so you will have to work with your DM to determine which 5 foot cubes are affected by these features.

Here is what a 15 foot spirit guardians and 30 foot Twilight Sanctuary look like from the side when you are on the ground, with the features affecting 6 and 12 ground adjacent cubes:

enter image description here

However, when you fly up 15 feet, notice that the number of ground adjacent cubes that would be affected decreases to 4 and 10:

enter image description here

Thomas Markov
  • 148,772
  • 29
  • 842
  • 1,137
  • I love the diagram, but I think it would be more beneficial if it was drawn with the perspective of the caster being in the middle of a square, and not at a connecting edge – MivaScott Mar 07 '22 at 19:52
  • 3
    @MivaScott That depends if you are actually using the grid rules from the DMG. If using the grid rules, then the point of origin is an intersection of squares, even if the area of effect is "centered on you". That said, I'm not sure the nuances of the distinction are material to the answer. – Thomas Markov Mar 07 '22 at 20:03
3

It depends on what you want to spend your time on

Both spells create an effect in a sphere around you (15 feet radius with spirit guardians, 30 feet with twilight sanctuary). The sphere will remain centered around you and if you move up, it will affect less and less squares on the ground.

Technically, Thomas Markov's answer gives you a view of what happens if you would move up 15 feet. If you moved up 30 feet, then the bottom of the spirit guardian sphere would not even reach the ground any more, with 15 feet of vertical space to move under your sphere. The twilight sanctuary might still affect maybe 12-16 squares, as it just touching the ground (you could calculate how many exactly by drawing or plotting, then counting cubes more than 50% affected. This might be called the technically correct answer.

My point however is: if you calculate this exactly and correctly, this is going to waste a lot of time during your play session. You are going to sit around doing trigonometry and calculating volumes, to determine how many squares are exactly affected. An hour later you have it all worked out, and finally play continues. Depending on the height and the radius of the spell, this is going to be different every time. How many are affected if you fly at 10 feet? At 20 feet? You'll need templates for each.

The light is not worth the candle. A simpler approach is to keep the game flowing and let your DM make a rough judgement call. Some things may be obvious, like a 15 feet sphere not affecting the ground if you are 30 feet up. In other cases, just use the full radius if you are low five to ten feet, or shave off a row of squares around the border, if in medium height. It will be technically incorrect, but it will be a heck of a lot faster, and you can get on with the game.

Or you can use theatre of the mind narrative combat. In this case, there is a table for estimating how many targets are affected on page 249 DMG. For a sphere or circle it is radius / 5 targets, so a 15-foot spirit guardians would normally affect 3 targets, a 30-foot twilight sanctuary would affect 6. Substract the recommended 1d3, when you are up in the air midways.

Nobody the Hobgoblin
  • 112,387
  • 14
  • 326
  • 684
  • Actually, the math isn't that hard. Looking at Thomas' answer, we can just guesstimate that for every 5ft you lift off the ground, you lose 5ft of radius. So at 10ft off, you'd lose 5ft of radius. At 15ft, you lose 10ft of radius. So at 20ft up, you lose 15ft radius or lose all effect of spirit guardians unless you have larger creatures or someone standing directly below the caster. – MivaScott Mar 07 '22 at 19:50
  • 2
    @MivaScott That's exactly my point, for practical purposes, a guesstimate is good enough. – Nobody the Hobgoblin Mar 07 '22 at 20:06
  • 3
    The spheres do center on an intersection of squares when using grid rules. "Choose an intersection of squares or hexes as the point of origin of an area of effect, then follow its rules as normal. If an area of effect is circular and covers at least half a square, it affects that square." – Thomas Markov Mar 07 '22 at 20:50
  • @ThomasMarkov, fixed -- learn something new every day. – Nobody the Hobgoblin Mar 07 '22 at 21:01
  • Tall creatures have parts of their body far from the ground, potentially sticking up into a sphere. Even Medium humanoids are usually about 5.5 ft tall. (Most non-human races being taller on average, I think, except for Small races.) So the area where the sphere touches the ground isn't necessarily the relevant question for whether a creature is affected. Computerized map tools like Talespire might be very good for this, letting you check a sphere in 3D space and seeing what minis it touches. (Vertical sphere range came up at least once in the actual-play season Dimension 20: The Seven) – Peter Cordes Mar 08 '22 at 09:45