What is the maximum distance you can cause damage from?

Question

What is the maximum distance a creature can cause damage from, without moving?

• This can be via any method (making an attack roll, forcing a saving throw, using an item), aside from the Wish spell.
• The creature inflicting the damage can receive any help from any number of creatures or use any number of objects.
• The distance is measured between the creature that inflicts damage and the creature that takes damage.

If possible, provide an example made without the use of any magic (anything that is stated to be magical, from any source), and an example using magic from any non-homebrew source.

Please state everything that contributes to each example. Such as if this is readily repeatable, or only so many uses per rest, or requires spell slots or item charges.

Answer 1

Depending on what you're asking, there may be no upper limit

The Pact of the Chain Warlock gets the following feature:

[...] Additionally, when you take the Attack action, you can forgo one of your own attacks to allow your familiar to make one attack with its reaction [...]

Note that there is no range restriction and so this could be done from any distance whatsoever. Thus one can allow their arbitrarily far away familiar to make an attack; perhaps this counts as an attack made over an arbitrarily large distance.

An alternative is using the dream spell

The dream spell states:

[...] Choose a creature known to you as the target of this spell. The target must be on the same plane of existence as you. Creatures that don't sleep, such as elves, can't be contacted by this spell [...]

On a failed save, echoes of the phantasmal monstrosity spawn a nightmare that lasts the duration of the target's sleep and prevents the target from gaining any benefit from that rest. In addition, when the target wakes up, it takes 3d6 psychic damage.

This gives you a way to deal 3d6 damage across any distance so long as you and the target are on the same plane. Notably this spell does require that you actually know the target

There are also the spells tsunami and storm of vengeance

These spells state:

A wall of water springs into existence at a point you choose within range.

A churning storm cloud forms, centered on a point you can see and spreading to a radius of 360 feet [...]

Both of these spells have a range of "sight" and so they could cross extreme distances especially using certain other features such as the Totem Barbarian's Aspect of the Beast feature having chosen Eagle:

You gain the eyesight of an eagle. You can see up to 1 mile away with no difficulty [...]

The UA Wildfire Druid has infinite range spells

The Wildfire Druid gains the Enhanced Bond feature which states:

[...] In addition, when you cast a spell with a range other than self, the spell can originate from you or your wildfire spirit.

Though the spirit must appear within 30 feet of you and only lasts for 1 hour, you could cast a spell from however far away the two of you can get. There is no limit to the distance between you and your wildfire spirit, and thus between you and your target.

An interesting case is the Open Hand Monk's Quivering Palm feature

This feature states:

[...] When you hit a creature with an unarmed strike, you can spend 3 ki points to start these imperceptible vibrations, which last for a number of days equal to your monk level. The vibrations are harmless unless you use your action to end them. To do so, you and the target must be on the same plane of existence. When you use this action, the creature must make a Constitution saving throw. If it fails, it is reduced to 0 hit points. If it succeeds, it takes 10d10 necrotic damage.

This is odd as it does require you to originally land some sort of attack on your target creature, but there after you have 17+ days to get as far away as desired from them and may then deal the 10d10 damage to them.

Answer 2

Infinite

A bag of caltrops costs 1 gp. It can, if properly used, deal 1 piercing damage to any number of creatures at any number of later times regardless of the distance between caltrop-deployer and caltrop-steppers-on. You don't need to be on the same plane, you don't need to be in the same timeline, you don't need to be alive, etc.

Even better, the spell Leomund's Secret Chest allows one to place an object on the Ethereal Plane such that it is "irretrievably lost". The Glyph of Warding spell lets you make an explodey chest that lasts until it is opened. In combination, this lets you possibly cause damage not only to someone who is infinitely far away from you but who is furthermore infinitely far away from everywhere you have ever been and ever will be.

In general, there exists a class of entities called 'traps' one of the primary features of which is the complete disconnect between the location of the trap-user and the location of the trap-victim when said victim is targetted for damage. 5e has lots of things that can function as traps, and many of them are extremely cheap and don't last any particular limited amount of time.

Answer 3

Note: This answer was written when the question was still asking for "the maximum distance a creature can attack from"; now that the question has changed to "the maximum distance a creature can cause damage from", this answer is somewhat limited to attacks. Rather than update my answer, I'll leave it in its current form in case anyone is interested in "attacks" specifically; otherwise, see Medix2's answer for the maximum distance one can cause damage from.

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Without magic, 600 feet, a Sharpshooter with a longbow

A longbow has a range of 150/600 feet, and the Sharpshooter feat (PHB, p. 170) includes this benefit:

Attacking at long range doesn't impose disadvantage on your ranged weapon attack rolls.

This means you can make a ranged attack against a target up to 600 feet without disadvantage. I am not aware of any class features or similar that would allow you to increase the range of your ranged weapon attacks. This would be "always on", so long as you have arrows.

With magic, 2 miles, a Lore Mastery Wizard/Sorcerer with the Distant Spell metamagic casting any ranged spell

This Unearthed Arcana article introduced the Lore Mastery arcane tradition for wizards, which includes the following class feature:

Alchemical Casting. At 6th level, you learn to augment spells in a variety of ways. When you cast a spell with a spell slot, you can expend one additional spell slot to augment its effects for this casting, mixing the raw stuff of magic into your spell to amplify it. The effect depends on the spell slot you expend.

[...]

An additional 2nd-level spell slot can increase the spell's range. If the spell's range is at least 30 feet, it becomes 1 mile.

Any ranged spell with a range of at least 30 feet, say fire bolt, then you can make a ranged attack roll at a target up to a mile away, assuming you have a clear path to the target and a way to see them at that distance (such as by multiclassing into Totem Barbarian to get the level 6 Eagle totem). This works so long as you have 2nd-level spell slots remaining.

If you multiclassed into sorcerer to get the Distance Spell metamagic, which says:

Distant Spell

When you cast a spell that has a range of 5 feet or greater, you can spend 1 sorcery point to double the range of the spell.

This can then be doubled to 2 miles. This is possible only if you have sorcery points to spend on the metamagic.

Alternatively, with magic, 2 miles and 20 feet, Sorcerer with Distant Spell metamagic casting meteor swarm

If we don't need it to be an attack roll specifically, then meteor swarm has a range of 1 mile, and affects a 40-foot radius area, so if cast at maximum distance, it could cause damage to a target that it 1 mile and 20 feet away from the caster.

Then you could increase this range to 2 miles, either by using the Distant Spell metamagic mentioned above. Doubling the spell's range allows you to damage a target up to 2 miles and 20 feet away. This is possible only if you have 9th-level spell slots to use, and sorcery points to spend on the metamagic.

Answer 4

Depends on how high you can get

If you are a creature with a natural flight ability, or have a flying mount, then fly up as high as you can and drop a rock on your target. If you can't fly, or can't fly without magic, arrange for your target to be at the base of the sheer side of a mountain and push a boulder off such that it will land on them.

Answer 5

The Way of the Open Hand monk's 18th-level Quivering Palm feature description states:

When you hit a creature with an unarmed strike, you can spend 3 ki points to start these imperceptible vibrations, which last for a number of days equal to your monk level. The vibrations are harmless unless you use your action to end them. To do so, you and the target must be on the same plane of existence. When you use this action, the creature must make a Constitution saving throw. If it fails, it is reduced to 0 hit points. If it succeeds, it takes 10d10 necrotic damage.

So as long as you're anywhere on the same plane, you can either kill someone or do 10d10 damage with this ability. You can do up to someone or something’s maximum hit points which could be a lot of damage depending on what creature you inflict this on.