Banneret (5A)

This is a Fighter subclass for 5A. This martial archetype is also known as the Banneret, this serves as the generic name for the Purple Dragon Knight archetype if you use it in campaign settings other than the Forgotten Realms or to model warlords other than Purple Dragon Knights.

A banneret is a knight who inspires greatness in others by committing brave deeds in battle. The mere presence of one in a hamlet is enough to cause some orcs and bandits to seek easier prey. A lone banneret is a skilled warrior, but a banneret leading a band of allies can transform even the most poorly equipped militia into a ferocious war band. A banneret prefers to lead through deeds, not words. As a banneret spearheads an attack, their actions can awaken reserves of courage and conviction in allies that they never suspected they had.

Greyhawk: This fits the royal and noble knights of many countries in the chivalrous west such as Furyondy, Veluna, and Keoland.

Source: Sword Coast Adventurer's Guide

Subclass features

Rallying Cry

When you choose this archetype at 3rd level, you learn how to inspire your allies to fight on past their injuries.

When you use your Second Wind feature, you can choose up to three creatures within 60 feet of you that are allied with you. Each one regains hit points equal to your fighter level plus your Charisma bonus (minimum 1 hit point), provided that the creature can see or hear you. Additionally, you can make a weapon attack as a part of the bonus action to use healing surge.

Social Graces

At 3rd level you gain proficiency in the Persuasion skill. If you are already proficient in it, you gain proficiency in one of the following skills of your choice: Animal Handling, Insight, Intimidation, or Performance.

Royal Envoy

Knights of high standing are expected to conduct themselves with grace.

At 7th level, you gain proficiency in the Persuasion skill. If you are already proficient in it, you gain proficiency in one of the following skills of your choice: Animal Handling, Insight, Intimidation, or Performance. your proficiency bonus is doubled for any ability check you make that uses Persuasion. You receive this benefit regardless of the skill proficiency you gain from this feature.

Royal Might

At 7th level, once per turn, when you damage a creature with a melee weapon attack, you can use a bonus action make that creature take a Strength saving throw, DC 8 + your Strength bonus + your proficiency bonus. On a failed save, you can push the creature 10 ft. away from you or make it fall prone.

Inspiring Surge

Starting at 10th level, when you use your Action Surge or Second Wind feature, you can choose one creature within 60 feet of you that are allied with you. If you used Inspiring Surge with Second Wind this must be chosen from the creatures that received healing from Rallying Cry. That creature can cast a cantrip or make one melee or ranged weapon attack with its reaction, provided that it can see or hear you.

Starting at 18th level, you can choose two allies within 60 feet of you, rather than one.

Bulwark

Beginning at 15th level, you can extend the benefit of your Indomitable feature to an ally. When you decide to use Indomitable to reroll an Intelligence, a Wisdom, or a Charisma saving throw and you aren't incapacitated, you can choose up to three allies one ally within 60 feet of you that also failed its saving throw against the same effect. If that creature can see or hear you, it can reroll its saving throw and must use the new roll and gains a bonus on the roll equal to your Charisma bonus (minimum +0).

Editor's Notes

The Banneret feels under-powered, so this is a boost.

Royal Envoy had its additional proficiency moved to a new level 3 ability to avoid characters going from no Persuade at all to expertise in persuade in one leap.
Rallying Cry got a small bonus to the hit points allies heal in order to give the class a Charisma incentive and to make the ability feel worthwhile at lower levels.
Royal Might is a new 7th level feature that allows you to knock enemies back or knock them prone. This gives the knight something that help himself rather than others.
Inspiring Surge got more targets, triggers on a healing surge, allows cantrips, and the level 18 version does not even require a reaction—a worthy capstone.