What spell targets count for the Graviturgy Magic wizard's Gravity Well feature?

Question

The Gravity Well feature from the Graviturgy Magic arcane tradition for wizards (EGtW, p. 185) triggers "whenever you cast a spell on a creature", and has an effect "if the target is willing to move, the spell hits it with an attack, or it fails a saving throw against the spell."

It's not clear to me what kinds of spells can actually trigger this feature.

Based on the singular phrasing of "on a creature" and the later use of the word "target", I would normally read this as only applying to spells that explicitly target creatures (and perhaps only those with a single target, in contrast to the phrasing of the Sculpt Spells feature of the Evocation wizard, for example).
However, spells that target a location can use the word target in a different sense (see What counts as a target for a spell?).

What's actually going on here?
Does this feature only work on targeted spells? Or does it function for area of effect spells as well? Or is this just an ambiguous phrasing that will rely on the DM's ruling?

Answer 1

Gravity Well probably works with areas of effect

The Graviturgy Magic wizard's Gravity Well feature states (EGtW, p. 185; emphasis mine):

You've learned how to manipulate gravity around a living being: whenever you cast a spell on a creature, you can move the target 5 feet to an unoccupied space of your choice if the target is willing to move, the spell hits it with an attack, or it fails a saving throw against the spell.

The bolded parts all show that the feature mentions a singular creature. But we cannot conclude whether this creature must be the only one targeted by the spell or merely a specific one. A GM could rule either that the use of the singular here means the spell must target only one creature or simply that the feature must target only one creature.

I recommend reading Thomas Markov's answer as it brings up some rather convincing arguments for why this feature should work with area of effect spells.

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It is woefully unclear whether an area of effect spell targets the creatures in its area of effect

Whether or not something like fireball actually targets the creatures in its area of effect is not particularly clear and we have a lot of questions on this and other related things:

• What counts as a target for a spell?
• Does a Morkoth's Spell Reflection work against AOE spells like Fireball?
• Spectator Spell Reflection for Hail of Thorns?

And many many related and linked question with questions related to and linked to those. People have argued fireball does not target creatures in its area of effect, and people have argued that it does; with all sides receiving numerous upvotes. Jeremy Crawford has held a surprisingly unwavering stance on the subject, but that doesn't mean much of anything (if anything at all).

At the end of that day, your GM will have to make a ruling about area of effect spells and what they consider to be their targets.

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Here are the wordings some features throughout the books use that your GM may find helpful in determining an answer:

[...] Durnan has advantage on saving throws against any spell that targets only him (not in an area of effect) [...]

[...] If the spell affects an area or has multiple targets, it fails and has no effect. If the spell targets only the snail, it has no effect on the snail and is reflected back at the caster [...]

[...] If an undead targets you directly with an attack or a harmful spell, that creature must make a Wisdom saving throw against your spell save DC (an undead needn't make the save when it includes you in an area effect, such as the explosion of fireball). [...]

[...] Immediately after a creature casts a spell that targets you or includes you in its area of effect [...]

Answer 2

Victims of AoE spells are unambiguously referred to as targets numerous times throughout the rules.

There are numerous rules in the PHB and DMG which specifically use "target" to refer to someone affected by an AoE spell. For example, in the PHB section "Targeting Yourself" (emphasis mine):

If you are in the area of effect of a spell you cast, you can target yourself.

Additionally, we see in the rules for Saving Throws (emphasis mine):

Many spells specify that a target can make a saving throw to avoid some or all of a spell's effects. The spell specifies the ability that the target uses for the save and what happens on a success or failure.

AoE spells are obviously in view here. Further, in the DMG's rules for Adjudicating Areas of Effect, we see (p. 249-250; emphasis mine):

If you would like more guidance, consider using the Targets in Areas of Effect table. To use the table, imagine which combatants are near one another, and let the table guide you in determining the number of those combatants that are caught in an area of effect. Add or subtract targets based on how bunched up the potential targets are. Consider rolling 1d3 to determine the amount to add or subtract.

[There is a table here]

For example, if a wizard directs burning hands (a 15-foot cone) at a nearby group of orcs, you could use the table and say that two orcs are targeted (15 ÷ 10 = 1.5, rounded up to 2). Similarly, a sorcerer could launch a lightning bolt (100-foot line) at some ogres and hobgoblins, and you could use the table to say four of the monsters are targeted (100 ÷ 30 = 3.33, rounded up to 4).

In the rules for using miniatures on a combat grid, we see the following about areas of effect (p. 251; emphasis mine):

The area of effect of a spell, monster ability, or other feature must be translated onto squares or hexes to determine which potential targets are in the area and which aren’t.

For a more specific example, the spell description of fireball even calls creatures it affects "targets":

A target takes 8d6 fire damage on a failed save, or half as much damage on a successful one.

This should work with Area of Effect spells.

The Graviturgy Magic wizard's Gravity Well feature says (EGtW, p. 195; emphasis mine):

You’ve learned how to manipulate gravity around a living being: whenever you cast a spell on a creature, you can move the target 5 feet to an unoccupied space of your choice if the target is willing to move, the spell hits it with an attack, or it fails a saving throw against the spell.

If you cast a spell affecting one or more creatures, you have cast a spell on "a" creature, so you may select "a" creature, who becomes "the" creature affected by the Gravity Well ability.

Notably, many features explicitly state when they only work for spells that target a single creature, such as the sorcerer's Twinned Spell Metamagic option:

When you cast a spell that targets only one creature and doesn’t have a range of self, you can spend a number of sorcery points equal to the spell’s level to target a second creature in range with the same spell (1 sorcery point if the spell is a cantrip).

To be eligible, a spell must be incapable of targeting more than one creature at the spell’s current level. For example, magic missile and scorching ray aren’t eligible, but ray of frost and chromatic orb are.

At least to me, this suggests that if Gravity Well only worked for single-target spells, it would say so explicitly, rather than using an indefinite article.