Oath of the Yojimbo.

Yojimbo are sworn to protect those to whom they dedicate their service, be it an individual, a group, or an entire nation. Though Yojimbo typically pledge their allegiance to a charge and accompany them until death, a defenceless soul might find the raking claws of a dodomeki halted inches from their face by the serendipitous intervention of a wandering Yojimbo paladin. These roaming saviours traverse the realms on an unrelenting quest to shield those who can’t protect themselves. Despite being in high demand— unshakeable loyalty is a coveted virtue—Yojimbo rarely pledge themselves to the wealthy or powerful. It’s said that a true Yojimbo has the value of ten sellswords in battle, and ten-thousand sellswords in spirit.

Level 1 Features:

Tenants of the Yojimbo.

The tenets of the Oath of the Yojimbo are unflinchingly resolute. They do not change or vary, no matter whom a paladin pledges to protect.
Protection. Be a shield to those who lack a shield of their own. Be the weapon that meets the blade of those who would slaughter the weaponless.
Strength. Grow strong for the sake of those who cannot. To shelter the vulnerable, one must have the power to hold back the storm.
Inspiration. Nurture the weak. Do not merely preserve the vulnerable; raise them up to be strong, so they might, in turn, protect others.
Self-Sacrifice. Wager everything for the safety of those who cannot fight. Nothing less is acceptable in the defence against tyranny

Level 3 Feature:

Oath Spells.

Each oath has a list of associated spells. You gain access to these spells at the levels specified in the oath description. Once you gain access to an oath spell, you always have it prepared. Oath spells don't count against the number of spells you can prepare each day.
If you gain an oath spell that doesn't appear on the paladin spell list, the spell is nonetheless a paladin spell for you.

Channel Divinity: Holy Ward.

You can use your Channel Divinity to perform a 1-minute divine ritual of protection, dedicating yourself to the service of a willing creature that stays within 30 feet of you during the entire ritual. The target becomes your ward for the next 24 hours, until you use this feature again, or until it dies. For the duration, your ward is immune to the frightened condition while you are conscious and within 60 feet of it. In addition, when your ward hits an enemy you can see with a weapon attack while within 60 feet of you, you can use a reaction and expend one spell slot to cause the attack to deal extra radiant damage to the target. The extra damage is 2d8 for a 1st-level spell slot, plus 1d8 for each spell level higher than 1st, to a maximum of 5d8.

Channel Divinity: Guardian's Intervention.

As a reaction, you can use your Channel Divinity to reduce the damage dealt by an attack to a creature you can see within 30 feet of you. When you do so, the damage the creature takes is reduced by a number of d10s equal to half your paladin level. If this feature reduces that damage to 0, the creature you protected can immediately use its reaction to make one weapon attack against the creature that attacked it.

Level 7 Feature:

Daring Protector.

Your divine power flows out from you. When an ally within 10 feet of you becomes the target of a melee attack, you can use your reaction to move up to your speed towards the attacker. If you end your movement within 5 feet of the attacker, you force it to target you with the attack instead.
At 18th level, the range of this feature increases from 10 feet to 30 feet.

Level 15 Feature:

True Guardian.

You are a master at providing aid in battle. You can take the Help action or use your Lay on Hands feature as a bonus action. In addition, when you take the Help action, the creature you helped can add your Charisma modifier (minimum of +1) to the next attack roll or ability check it makes within the next minute.

Level 20 Feature:

Ultimate Defender.

You can harness extraordinary defensive power to protect those around you. As an action, you become an avatar of protection, gaining the following benefits for 1 minute or until you are incapacitated:
-Creatures of your choice other than yourself that are within 10 feet of you have a +3 bonus to AC.
-If the creature you have designated as your ward with Holy Ward falls to 0 hit points while within 60 feet of you, you can use your reaction to cause it to fall to 1 hit point instead.
-Your melee weapon attacks deal an extra 2d8 radiant damage while your ward is within 60 feet of you.
-You can use Guardian’s Intervention without expending a use of your Channel Divinity.
Once you use this feature, you can’t use it again until you finish a long rest, unless you expend a 5th-level spell slot to use it again.