Momentous Combatant

Momentous Combatants harness their natural speed and knowledge of physics to enhance their fighting. The strength behind their blows surprise and astound. These warrior-intellectuals find the sweet spot between Mass and Velocity - heavy enough to generate power, but not so heavy as to limit their movement. 

Movement, Mass, and Momentum

Your unique fighting style requires particular attention to Encumbrance and Movement rules.

Encumbrance. If you carry weight in excess of 5 times your Strength score, you are encumbered, which means your speed drops by 10 feet. If you carry weight in excess of 10 times your Strength score, up to your maximum carrying capacity of 15 times your Strength score, you are instead heavily encumbered, which means your speed drops by 20 feet and you have disadvantage on ability checks, attack rolls, and saving throws that use Strength, Dexterity, or Constitution. Additionally, you cannot use the features for this subclass. 

Size and Strength. Larger creatures can bear more weight, whereas Tiny creatures can carry less. For each size category above Medium, double the creature's carrying capacity and the amount it can push, drag, or lift. For a Tiny creature, halve these weights.

Movement. For the sake of features in this subclass, movement refers to distances walked, fallen, or flown and does not include distances teleported, carried, climbed, or swam (Use DM discretion.)

Saving Throws. Some of your momentous strikes require your target to make a saving throw to resist additional effects. The saving throw DC is calculated as follows:

Momentum save DC = 8 + your proficiency bonus + your Strength or Dexterity modifier (your choice)

Hit and Run

Beginning when you choose this archetype at 3rd level,  you can use your speed to generate power in your strikes. When you make a melee attack after moving at least 10 feet, you can apply additional force damage equal to your DEX modifier (minimum +1). 

Move Fast, Hit Hard

Starting at 7th level,  you can now use momentum to increase the damage of your blows. Once per turn when you take the attack action, your first melee attack gains 1d4 force damage per 15 feet of movement taken before the attack (rounded down). The damage increases to 1d4 per 10 feet at level 10, and 1d4 per 5 feet at level 15.

Knock Back

Beginning at 10th level, when you hit a creature with a melee attack, you can expend one use of this feature to attempt to drive the target back. You add 1d6 force damage to the attack’s damage roll, and if the target is Large or smaller, it must make a Strength saving throw. On a failed save, you push the target up to 15 feet away from you. This feature can be used twice per short rest. 

Unencumbered Movement

Starting at 15th level, your speed increases by 15 feet while you are not Heavily Encumbered.

What Comes Up

At level 18, your mastery of physics taught you new ways to take advantage of your mass when leaping, jumping, and falling. Once per turn, when you move at least 15 feet, you may make one Flying Strike attack as part of your attack action. After your attack roll, make an Athletics or Acrobatics check (DC20). On a failure, you deal one standard melee attack. On a successful hit, for every 20lbs you weigh and carry, your Flying Strike attack does 1 additional point of force damage. The target must also make a Strength saving throw or be knocked prone.