Dark Soul

I don't have lore to put here, dark souls explained it better.

Estus Flask

At 3rd level, you gain a golden flask that you can drink from as a bonus action. This replaces the second wind ability. The flask has an amount of charges equal to half your fighter level plus your proficiency bonus. Drinking from the flask causes you to regain hit points equal to half your fighter level in 1d4+1. For example, a 4th level fighter would have 4 flasks that each heal you for 2d4+2. 

Dodge Roll

When you gain this feature at 7th level, you learn how to effectively dodge out of harm's way. When a creature makes an attack against you (melee or ranged), you can use your reaction to dodge roll. Make a dexterity save with a save DC determined by this description:

8 + enemy attack modifier.

If you succeed on dodging an attack, the attack deals no damage and you move 5 feet to either your left or your right. This movement does not provoke opportunity attacks. If you fail  you still take damage, but you do get the movement from the roll.

Every time you do this, roll a d20. If you roll a number equal to or lower than the amount of times you have done this before taking a short or long rest, take 1 level of exhaustion. This number resets when you take a rest.

Fast Flask

Beginning at 10th level, you gain the ability to drink estus in response to taking damage. When you are hit by an attack from any distance, you can use your reaction to drink from your estus flask. 

Recovery

On your turn, you gain the ability to remove 1 level of exhaustion by expending two charges of your estus flask as a bonus action.

Soul of Cinder

At 18th level, you attain the pinnacle of resilience in battle. At the start of each of your turns, you regain hit points equal to your Constitution modifier if you are not at full health.