Oath is very simple. A vow is made, and so long as that vow isn't broken, a Knight has the courage to perservere with great power.

With Oath you will be reduced to 1 HP anytime you are dealt a blow that would usually deal mortal damage. Any damage taken at that point would then put you in Memento Mori as usual.

An Oath can be as simple as "Thou shall not steal". You can make your own Oath. Here's some examples:

• Thou shalt not steal - You may not take an item that isn't yours.
• Thou shalt not lie - You may only ever speak with truth.
• Thou shalt not attack dishonorably - You may never attack something surprised or helpless.
• Thou shalt not upset one - You must be strictly diplomatic to those you meet.

Breaking Oath will have you lose its benefits. Many feats change their effects if Oath is broken.

The Knight is trained in combat more than anyone else, applying trained strategy to their combat. This composes of different Stances meant for different encounters, giving The Knight different advantages. The Knight is able to change Stances as a Bonus Action. Most Stances last indefinitely. A full list of Stances can be found here: Stances

When under Oath, you may choose one round per Battle to completely negate damage.

With Oath broken, you do not take hits with grace. You can take as much mortal damage as you'd like, and still live for multiple rounds until the battle ends.

You've developed a fluid speech pattern due to your upbringing. With Oath, gain +3 Persuasion.

With Oath broken, a lie seems so trivial. Gain +3 Deception instead.

Your fortitude has become strong due to warfare. When under Oath, if your Resolve is being tested, you may add your Composure score to your roll result.

With Oath broken, you may instead cope by lashing your trauma on others. You may choose to force someone else to have their Resolve tested instead of yourself.

Gain an extraordinary burst of energy in times of great need. When under Oath, gain an extra Main Action once every Battle.

With Oath broken, you instead put fear in opponents to drain them of vigor. You may choose to prevent an enemy from taking an action, once per round.

You've witnessed many comrades beside you die over, and over. It breaks you down, but makes your will stronger. With Oath, anytime an ally dies you may add a point to either a MND or EGO Skill.

With Oath broken, you use it to push your tenacity. Instead, add a point to a PHY Skill, or subtract a point from an EGO Skill.

You fight majestically, as though it were an art-form. With Oath, for every attack you dodge, gain another Attack Die for your weapon. If you are hit or the battle ends, you lose your Attack Die.

With Oath broken, pain in battle only excites you. Anytime you take damage, gain an Attack Die. If you back away from battle, become Unconscious, or the battle ends, you lose your Attack Die.

Inspiring words of courage can go a long way. With Oath, you may give (relatively meaningful according to the GM) words of courage to give anyone a 1D6 temporary HP buff.

With Oath Broken, helping the weak in a fight is merely a fools move. You can instead demoralize someone once they've blundered to give yourself a 1D12 temporary HP buff.

The spoils of war act as a showcase of your valiant lifetime. You may choose to sever and keep a specific body part of slain foes as a trinket. Every 3 trinkets you collect gives you a free point to put into any Skill.

Your Knight training has taught you quite a bit about Health in combat. With Oath, you may resuscitate an ally that has just recently died or gone unconscious (so long as they could reasonably make a recovery) back to half HP, at the cost of 1D6 of your own HP.

With Oath broken... Sometimes it's better to get it over with, and put a poor sod out of their misery. If you finish off an ally yourself, you may steal one Class Feat of their own.

A Knights death is one of significance. Something to not be forgotten. With Oath, dying may give +1 Attribute point to any ally with a positive relationship with The Knight.

With Oath broken, you will burn your mark into this world past death. Dying, even by suicide, gives you the opportunity to curse anyone, any group, or anything with some effect. The GM will advise what's a valid curse and what isn't.