Momentum: Every time you damage a creature with a weapon attack, you gain 1 point of momentum, up to a maximum of your Fighter class level. If the attack was with a 2 handed weapon, you instead gain 2 points of momentum.
If you end your turn without attacking a creature, you lose 1 point of momentum until you reach 0.
You can expend 3 points of momentum to deal an additional set of weapon damage dice; if the weapon is light, it only costs 2 points of momentum.
Backbone: Every time an attack hits you, you gain 1 point of Backbone; if the attack misses you, you gain 2, up to a maximum of your Fighter class level.
If you end your turn without being attacked since the end of your last turn, you lose 1 point of Backbone until you reach 0.
You can expend 3 points of Backbone to Block with a shield as a reaction to an attack, adding your proficiency bonus to your AC against that attack.
You can expend 3 points of Backbone to Parry with a melee weapon as a reaction to a melee attack. Roll an attack with that weapon; if it beats the enemy attack roll, the attack misses.
You can expend 3 points of Backbone to Riposte with a light or finesse melee weapon as a reaction to a melee hit. Make an attack on the target with that weapon.
If you have two weapons equipped and your Riposte beats the enemy attack roll, it also counts as a Parry.
You can expend any number of points of Backbone to reduce the damage of a hit an equal number of points, up to a maximium of half of the damage from the hit.
...
naw, too fiddly.