Kinslayer

A Kinslayer are those that have an established link to a God or Goddess. This devotion has given them various boons, most notably the ability to act without fear. Their name comes from their original purpose, to avenge a fallen home, or avenge a fallen love one. 

Abjuration of Sanzu

When you choose this architype at 3rd level, you gain the ability to put off death, if only momentarily. When you start your turn at 0 hit points, you can choose to use this feature to gain hit points equal to your Constitution modifier times your Fighter level. This can be used once per long rest. Also, longswords now count as finesse weapons when wielded by you.

Duelist's Poise

At 7th level, when you take the attack action, you can make an addition attack. This additional attack deal an additional 1d6 damage of the weapon. While not being unconscious, you cannot be knocked prone as your reflexes have adapted to react to a change in environment. 

Penance

At 10th level, when an enemy reduces you to 0 hit points or kills you, you can sense their location for 24 hours after being revived or regaining consciousness. Any effect that would disguise them, hide their presence or other wise make them not noticeable is not immune to this ability. In addition, you gain advantage on attacks against this target for the duration.

Mortal Insight

At 15th level, you become tranquil with the machinations of death, divinely inflicting hesitation upon your foes. While you are conscious, you are under the effects of the Sanctuary spell.  These effects do not fade if you make attacks or other wise harm a creature. After an attack successfully hits you, this affect is suppressed until the start of your next turn. The saving throw for this ability is 8 + Constitution + proficiency.

Immortal Tether

Starting at level 18, you can use your Abjuration of Sanzu feature twice per long rest. In addition, you can choose to make saving throws that would be made at the end of your turn at the beginning of your turn and vice versa. You also gain resistance to bludgeoning, slashing and piercing damage.