Credit

This homebrew is taken verbatim from a post by u/Sir_Platinum on Reddit titled "Three Halflings in a Trenchcoat V2 - Electric Boogaloo". Permission has been obtained to adapt the formatting and publish here. The image is the one that accompanies the post and was drawn by redditor u/maligapoo.

A note on the build

This archetype is a special variant that must be chosen from Level 1. In order to fit within the levelling requirements for 5e Fighter builds (and D&D Beyond homebrew requirements), the various Level 1 features have been amalgamated and moved to Level 3 for this build. For this reason, it is only recommended to start using characters with this build at Level 3 (unless intending to start as a single halfling and acquire partners at Level 3).

Halflings chosen are considered as one entity, so must be the same subrace and follow the same build path.

I have also done my best to adapt the various rules to the D&D Beyond system to automate where possible, but some aspects are either not possible or beyond me. Do please read the the notes for each ability thoroughly and discuss with your DM.

Class notes

(taken from clarifications by Sir_Platinum on Reddit)

• I intend this character to be played as a pure fighter, no multiclassing.
• You could play this with any small race, I chose halflings because they have a +2 to dex racially, and if anyone can pull it off, they can. I'd recommend a minimum dex score of 14 or 16 to prevent it from being the dump stat.
• Remember, this is one fighter. Not a unit, or a squad. One fighter, 3 attunement slots, one standard HP pool. You get a +1 to AC because I felt like it. Buff, nerfs and damage is counted as if for a single target. The halflings swear an oath to not break formation for more than moments at a time.
• All halflings are the same race and racial bonuses don't stack.
• Only light weapons are allowed for the build as they are the only type that can be easily concealed, and the inertia won't put the top hobbit off balance.
• No shields, regular, or two handed weapons. This puts your weapons at a max of 1d6.
• Light thrown and ranged weapons, and blowguns are fine but since you can't aim that well when stacked up so you get disadvantage.
• 3 halflings count as a medium size character. Steve makes them a large size. You have an advantage on grappling, and all arms must make the grapple. Enemies can only disarm the top halfling.
• For price of power, no heavy armour and no dex bonuses from medium armour.
• Multiform Technique before level 10 cannot be used in front of a hostile witness. That means if there are two enemies, you cannot use it on one unless you blind, distract, isolate, or incapacitate the other. As for the person you're attacking being a witness, no one is going to believe the one lunatic who says a guy became three tiny guys and stabbed him 20 times. (Your DM can add an optional rule to silence the victim if he wants)
• Snitches get stitches just negates the witness penalty of the multiform technique.
• Uncanny valley is worded so to prevent the character from intimidating a PC from the party.
• Steve adds an extra pair of arms, so more stabby stabby. Yes, Steve also stacks with Haste and Action Surge, just like the original halflings.
• As a final note, yes, this archtype is very strong as an attacker. But the disadvantages are pretty significant and as long as you don't minmax you can have a lot of fun with him. I hope you enjoy this!

 

True Devotion

True Devotion

You must choose this path from the 1st level instead of the 3rd. 

All is One

All the halflings are considered as a single creature for the purpose of health and damage taken. Your size is medium.
You gain a +1 to AC

Secrets of the Teeny Tiny

This path would be far too powerful if unleashed upon the world. You must remain clandestine and hide your true nature to all but your most trusted so that when the time comes you may strike true.

• You can only wield light melee weapons as they can be easily concealed
• You can not wield shields.
• Darts, blowguns and other easily-concealed ranged weapons with the light property may be used for ranged attacks.

The Price of Power

Your dexterity is focused on keeping balance.

• All dexterity checks or saves or attacks have a disadvantage.
• Any ranged attack made is made with a disadvantage.
• You cannot add a proficiency bonus to any dexterity skills.
• Finesse weapons cannot use dex properties.
• Medium armour receives no bonus from dexterity.
• Your movement speed is decreased by 5 feet.

Power of Six Arms

They say two heads are better than one, and six fists are certainly better than two.

• Your fighter makes three attacks instead of one, one for each halfling.
• This stacks multiplicatively with extra attack.
• You can use action surge or haste with this feature as well (e.g. A level 5 TTF can make 6 attacks per turn, 12 with action surge)

Multi-Form Technique

Starting at the 7th level, at the start of your turn, you may choose to take a calculated risk to split up into three halflings and surround an attacker to make an attack. This feature can only be used twice per short rest, and only if there are no hostile witnesses. You must resume your base form at the end of your turn.

All attacks made against the target have advantage, and you do not suffer the price of power.

 

Notes:

Multiform Technique before level 10 cannot be used in front of a hostile witness. That means if there are two enemies, you cannot use it on one unless you blind, distract, isolate, or incapacitate the other. As for the person you're attacking being a witness, no one is going to believe the one lunatic who says a guy became three tiny guys and stabbed him 20 times. (Your DM can add an optional rule to silence the victim if he wants)

Snitches get Stitches

Starting at the 10th level any witnesses to the Multi Form Technique become terrified of the consequences of snitching. You can use this feature anywhere. Your secret is safe.

Uncanny Valley

At the 15th level., you have mastered the art of balancing three people in a trenchcoat. Your movements look almost real but not quite, causing a feeling of unease. You gain advantage on all intimidation checks to anyone who hasn't seen through your disguise.

The One they call Steve

At the 18th level, you call upon your buddy, Steve, to aid your journey. You are now four halflings in a trenchcoat.

Where you would attack thee times, you now attack four. This continues to work with Action Surges / Haste etc. All other statistics (including HP, attunement etc. remain the same and are unaffected).