Can weapons with Reach be used to attack “through” willing allies?

I’m picturing the Greek Phalanx formation, where soldiers were arranged in rows and the men in Row B or even Row C could attack the enemy by thrusting their spears between the soldiers in Row A.

Can you do that with a Reach weapon in DnD 5e? Attack an enemy even though there’s an ally (or even a row of allies) directly between you and them?

Is the stone giant’s 15′ reach with the greatclub an error? [duplicate]

The standard stone giant stat block has a reach of 15′ with its greatclub melee attack. However, I can see no reason from the rules or description for it to be so, instead of the standard 10′ reach of all other huge giant melee weapon attack. Is this a typo that has not yet been caught, or is there some other explanation for this longer-than-usual reach?

Does anyone else think Stone Giant’s 15′ reach greatclub is an error?

All of the basic Monster Manual giants have a melee weapon attack with reach of 10′, which essentially comes from their Huge size. But the Stone Giant has a reach of 15′ with it’s greatclub, which is farther than the reach of a Hill Giant’s greatclub, the Cloud Giant’s morningstar, the Frost Giant’s greataxe, or the Fire or Storm Giant’s greatswords. The huge Cyclops, with 1 more hit die than the Stone Giant (thus at least the same size), also has a greatclub with reach 10′.

I don’t see any reason for this. The Stone Giant is not depicted as having disproportionately long arms, and it’s only in the middle of Giant heights; Frost, Cloud, and Storm Giants are all taller. Nothing in the description mentions Stone Giants carrying a particularly long club or having a talent for swinging it further. Rather, the description talks about their skill at throwing rocks. The only monster I know of that is specified as having longer reach attacks ("long-limbed") is the PC version of the Bugbear in VGtM.

None of the previous editions (AD&D, 3.5 or 4th) give the Stone Giant extra reach with a club.

So my suggestion is that this was a typo that was never caught & corrected. The reach of this attack should be 10′ like that of any other huge Giant.

Can you Ready an attack with the trigger ‘enemy enters my reach’? If so, will you interrupt their movement on a hit?

Without using any feats, can a player with a reach weapon set that weapon to receive a ‘charge’ by the enemy, attacking them when they enter range? Or even a non-reach weapon? That is, can a player commit to using their attack action when an enemy crosses an arbitrary line with their movement? (Examples: Ready my glaive to attack when the orc gets 10′ away from me. Ready my shortbow to attack when the dragon enters 80′ from me. Ready my dagger in case the kobold comes adjacent.)

If this is possible, and the player’s attack hits, does it have any effect on the enemy’s remaining movement or other actions?

I think the answers are yes, and no, respectively.

Is a creature’s reach linked to the reach of its attacks?

This is an issue I’ve seen coming up with the addition of the Eldritch Claw Tattoo in Tasha’s Cauldron of Everything, though there seem like there were possible cases of it before.

As far as I can tell, every character starts with a reach of 5 feet. If they are wielding a weapon with the Reach property this explicitly increases the reach of both their attacks, and their reach for the purposes of being able to perform an opportunity attack reaction, by five feet:

This weapon adds 5 feet to your reach when you attack with it, as well as when determining your reach for opportunity attacks with it.

However, an Eldritch Claw Tattoo’s Eldritch Maul effect doesn’t mention opportunity attacks in the same way, it only mentions the range of your attacks:

As a bonus action, you can empower the tattoo for 1 minute. For the duration, each of your melee attacks with a weapon or an unarmed strike can reach a target up to 15 feet away from you, as inky tendrils launch toward the target.

There is a similar case for the playable Bugbear race from Volo’s Guide to Monsters, which has the long-limbed trait:

Long-Limbed. When you make a melee attack on your turn, your reach for it is 5 feet greater than normal.

In both cases it sounds like the additional reach only applies when you actually attack; it’s unclear whether your reach is also increased for triggering an attack of opportunity or not.

I think the tricky point is that the reach that determines whether you can make an opportunity attack, occurs before you’re actually making any kind of attack roll (i.e- it determines whether you can use your reaction or not), whereas the latter two quotes suggest your reach is only increased when actually attacking (about to make the attack roll). As far as I can tell (though I may have missed it) the rules don’t state that your reach is based on your melee attack reach, it just happens to be convention that some effects that increase one, also increase the other.

This feels like it might be a bit of a weak distinction, but it also feels very strange that a temporary increase in range should render a character unwilling to strike at an enemy that they would have attacked just a moment before.

So my question is, is there anything in RAW that makes clear that Eldritch Maul, Long-limbed and so-on should also apply to reach for the purposes of triggering an opportunity attack, or am I correct in thinking these may be separate?

Does the reach increase of the Eldritch Claw tattoo stack with Fangs of the Fire Snake?

The Eldritch Claw tattoo released in Tasha’s Cauldron of Everything includes the Eldritch Maul ability which grants the following benefit:

For the duration, each of your melee attacks with a weapon or an unarmed strike can reach a target up to 15 feet away from you, as inky tendrils launch toward the target.

The Fangs of the Fire Snake elemental discipline also grants the following benefit:

Your reach with your unarmed strikes increases by 10 feet for that action, as well as the rest of the turn.

After activating Eldritch Maul and using Fangs of the Fire Snake what is the reach of my unarmed strikes? Would it be 25 feet or would it be 15 ft?

Ways to extend my natural (non-weapon) reach?

I have a character who has taken Inhuman Reach from Lords of Madness and Deformity (Tall) from Book of Vile Darkness, and is two levels away from warshaper 3rd and the morphic reach feature from Complete Warrior. I have the long arm fiendish graft from Fiend Folio. All told, I’ll have a natural reach of 25 feet.

I want more.

What other options—aside from the obvious one of growing in size myself—offer more bonuses to reach? I’m aware of this question seeking ways to increase reach for unarmed strikes only, but again, that’s unarmed strikes only—I want this for everything (and actually the atavist option in the accepted answer is not useful to me, as I’m using claws rather than unarmed strike).

Non-epic 3.5e material (including 3.5e-legal 3e material) from Wizards of the Coast sources and/or Dragon or Dungeon magazine are acceptable. Homebrew and 3rd-party material (including 3rd-party material that licenses the D&D logo) is not. Epic material may be presumed to not exist.

Feats and class features are ideal. Meeting prerequisites may be left as an exercise to the reader, so long as they do not require an epic character or epic stats.

Items are also welcomed for this purpose. Spells and other limited-duration effects (including item effects, for activated items) are only acceptable if they last a day or more. Persistent Spell and other ways of persisting effects are not acceptable. Abusing polymorph any object’s poorly-defined duration rules is also not allowed.

For that matter, turning into another creature with longer reach is not acceptable. I want to add the bonus to my own reach, not turn into something else. Size increases are also unacceptable—I’ll no doubt be doing that too but that’s a separate concern.

Infinite and arbitrary loops, manipulate form, “unleveling,” and outside assistance are all banned as well.