How does targeting work when casting the Call Lightning spell through Glyph of Warding?

Question

The Call Lightning spell targets an area, then the caster chooses a point in that area and anybody within a 5-foot radius of that point is damaged. Then on each of their turns, the caster can use an action and choose another point for another bolt of lightning.

Casting it through a Glyph of Warding has the benefit of not using concentration and getting a whole 10 minutes (100 turns) of duration. But would it work?

Glyph of Warding works with spells that target area by autotargetting the area centered on the triggering creature - that's fine, the cloud appears above an enemy. But then what happens - would the glyph also choose the point in that area to target that enemy? Would the glyph do it every turn? What if the enemy that triggered the spell died on the second turn and there's still 98 turns more of the spell duration - would the glyph target another enemy?

Or maybe, since the caster is still "me", would I get to choose the points where the lightning falls each round?

Answer 1

I don't think Call Lightning works with Glyph of Warding

Glyph of Warding's Spell Glyph feature states that the spell you select:

The spell must target a single creature or an area.

Call Lightning states:

When you cast the spell, choose a point you can see under the cloud. A bolt of lightning flashes down from the cloud to that point.

So while the cloud itself fills an area, the lightning that is getting called targets a point, which is neither an area nor a creature. Spells like Hypnotic Pattern, Faerie Fire, Alarm, and Gust of Wind are examples of spells that affect an area without using a reference point.

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However, Medix2 raises a worthy follow up question. It is much more common for area effect spells to have their positioning defined in relation to a point and it is conceivable that many of these spells were intended to work with Glyph of warding.

If we use this looser interpretation that allows the use of AoE spells where a point is referenced, Call Lightning still poses problems.

Glyph of warding says the area of effect must be centered on it. But the cloud is 10 feet tall by 120 feet wide and:

The spell fails if you can't see a point in the air where the storm cloud could appear (for example, if you are in a room that can't accommodate the cloud).

This means that many of the places you might cast Glyph of Warding would cause Call Lighting to fail.

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If it's cast in a place that doesn't cause this problem, there's also the fact that you need to see the point where the lighting strikes. While technically the spell doesn't say the storm cloud blocks line of sight, the rules for vision and light say:

A heavily obscured area--such as darkness, opaque fog or dense foliage--blocks vision entirely.

Normally, the cloud is "100 feet directly above you" which would not interfere with seeing the location struck by lightning. But when it is right on top of and covering the only targetable area as per Glyph of Warding's requirements (to wit: "If the spell affects an area, the area is centered on [the creature that triggered the glyph]."), that means you can't see the point you want to target and therefore can't call the lighting onto it.

So, one way or another, it is difficult to see how the two spells could work together.

Answer 2

You get between zero and one bolts.

Rykara's answer raises valid concerns about using call lightning this way at all. Still, a very generous reading of the "creates harmful objects or traps" language in glyph of warding would allow the initial lightning bolt to hit the creature that triggered the glyph.

After that, call lightning would normally let the caster call down more bolts:

On each of your turns until the spell ends, you can use your action to call down lightning in this way again, targeting the same point or a different one.

"You" here refers to the spellcaster, which is the glyph, rather than the glyph's creator.

Why? Because it's the glyph's mechanics that actually say "the spell is cast", and at that time the glyph's creator doesn't do anything. They don't have to expend a spell slot, or have the spell prepared, or concentrate, or be in range, or choose targets, or even be alive at all. The glyph does all of that for them. The original caster has no connection to the spell at this point; they can't even dismiss it by dropping concentration.

Since the glyph doesn't get turns and can't take actions, it can't direct additional bolts.