Banner Knight

This sub-class is a support based Fighter that uses their abilities to aid allies in combat. This is something that Fighters on their own do not do but I find it an interesting concept that opens up more versatility for the class. Firstly some advice on playing the subclass, Charisma should be one of the highest if not the highest stat you have as most of your abilities and features rely on it. This also means that in addition to focusing on Strength and Constitution you need three decent stats to pull this subclass of properly. For game play this sub-class is heavily support orientated and if you are a player that likes to focus on themselves in battle this is not the subclass for you.

Call to Arms

When you choose this archetype at 3rd level, you learn how to inspire your allies to fight for longer. As a Bonus Action you choose up to three creatures within 30 feet of you that are allied with you. Roll 1d8 and add your Charisma modifier, the chosen allies gain temporary hit points equal to the result provided that they can see or hear you. This effect lasts 1 minute and ends if you are incapacitated. The amount of uses for this feature is equal to your Charisma modifier and you must complete a long rest to regain any expended uses. At the levels 7, 10 and 15 you can target one extra ally and roll an additional 1d8 when using this feature. 

Knight of Chivalry

At 7th level, you gain proficiency in Charisma saving throws as well as the Persuasion skill. If you are already proficient in Persuasion, 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.

Courageous Leadership

At 10th level you can encourage your allies to strike true or avoid hostile effects with your leadership. When an ally within 30 feet of you makes an attack roll or saving throw you can expend your reaction to add your Charisma modifier to that roll provided they can see or hear you. This ability can be declared after the die is rolled, but before the outcome is determined. The amount of uses for this feature is equal to your Charisma modifier and you must complete a short or long rest to regain any expended uses. 

Rallying Charge

Starting at 15th level, when you use your Action Surge feature, you can choose creatures (up to your Charisma modifier) within 30 feet of you that are allied with you. The selected creatures can make one melee or ranged weapon attack with its reaction, provided that it can see or hear you. 

Superior Call to Arms

At 18th level you improve your Call to Arms feature considerably with the following effects. All allies affected by this ability gain Advantage on their next attack roll, ability check or saving throw. They are also immune to being Charmed or Frightened until the end of your next turn. If they are already under one of these effects when this feature is activated then they can re-roll the saving throw and add your Charisma modifier. On a pass they are no longer under the Charmed or Frightened effect and are immune until the end of your next turn.