Valkyrie

The subclass Valkyrie focuses on the honor and morality of combat.  In the eyes of a Valkyrie, you must show mercy when you can, and fight only when provoked.  While in battle, a Valkyrie will protect their allies as themselves and will not flee until the fight is finished.  They accept defeat with grace and honor and do not gloat in victory.  Valkyries live by a code of ethics:  Be loyal, fight smart, and show mercy. 

Honorable Attack

Tapping into your inner righteousness, you gain extra motivation when you are fighting a creature of any evil alignment.  Beginning at 7th level, any time you attack an evil creature with a weapon, you can add 1d4+STR modifier to the damage if the weapon uses strength, or 1d4+DEX modifier if the weapon uses dexterity.

Merciful Knight

Mercy being one of the core tenants of the Valkyrie subclass, you benefit morally from showing mercy in battle.  Starting at 10th level, when an opponent surrenders or is incapacitated and you choose not to continue to attack it, you have advantage on any INT, WIS, and CHA checks for the next 24 hours.  In addition, for the next hour, you have advantage on all WIS (Insight) checks to interrogate the creature.

Defense of Friends

Protecting your friends is a major part of walking the Valkyrie path, and you have an urge to fight back when you see your friend being attacked.  Starting at 18th level, for one round, you have advantage on weapon attacks against creatures that attacked one or more of your friends on its most recent turn.

Religious Backstory

As a Valkyrie, your background was somewhat religious, and most people saw you as a kind person and a good friend.  Starting at 3rd level, you gain proficiency in either Religion or Performance, your choice.

Performance

You gain proficiency in performance.

Religion

You gain proficiency in religion.

Holy Strike

You learn to channel your righteous and religious energy into a very powerful weapon attack.  Starting at 15th level, once per long rest, when you attack with a weapon, a few bolts of lightning shoot out of your weapon and your target takes an extra 8d6 lightning damage and is blown 40 feet away and knocked unconscious.  You can't do this to the same enemy twice, and in addition to taking a long rest between doing this attack, you must take 10-20 minutes of meditation and holy rest before you can do this again.