The Frail

This class is made for an undead character, however it is possible to be played with a non undead if you choose. Please consider your backstory or abilities if you wish to use this subclass as some of the abilities won't make functional sense. Although, if your a war forged this is completely sidestepped and please disregard my previous statement. If you choose to play any other race it may be gruesome. You can alter some of the descriptions and become a Portal Fighter instead to better fit a character

Guile

You gain the ability to make your body sentient. You gain points called Guile to use these skills, You start with 5 points of Guile , you gain 2 additional points of Guile at levels 7, 12, 16, 18 . Guile is recovered upon performing a long rest. You apply the finesse (weapon) trait to all non heavy or two handed weapons, dexterity as your attack  modifier.

Unnatural reach

you remove an arm from its socket and use it to extend your melee range by 5ft (weapons with reach also benefit from this)  by holding your dominant arm in the other hand with your weapon (expends 1 Guile and the effect remains until the end of your turn) you may expend 1 additional Guile to disarm the target if they are holding a weapon; they are large or smaller

Bone Hop

(As a reaction) You have the ability to split apart your bones between the joints before you're struck with a/an (non saving throw) attack, you can expend 1 (up to 3) Guile to reduce the roll of a creature targeting you by 2 (up to 6) before the attack has occured.

Parting Gift

 (passive) your cold hands reach around the throat a creature you grapple and sever upon succeeding a grapple, after grappling an enemy, you may expend 1 finesse to keep the enemy grappled while you are free from the target creature. Must maintain 30 ft within target Effect ends when range is exceeded. The effect lasts until the start of your next turn and can be refreshed each turn by expending 1 finesse. Additionally,  you may only use Necrotic Bite and Ranged Choke as your attack actions as long as an enemy is grappled this way.

Necrotic Bite - (Attack 5ft) you bite your jaws down on a target creature dealing 1d4 piercing damage and 1d10 necrotic damage. (you can only use this attack while Parting Gift is active unless specifically stated.)

Ranged Choke - (Attack 30ft) Usable as a bonus action. This attack ALWAYS succeeds. (target creature must be afflicted by Parting Gift) you choke the target grappled creature  for 2d8 force damage. (You can only use this attack while Parting Gift is active)

Cadaver Collector

Your eccentric fighting style leaves you in lack of bone matter. Luckily, you're in no short supply. Cadaver Collector - After you kill a creature gain 1 Guile

The Wretched Mass

You transform into a ball of bone and steel. You gain the following benefits and attacks:

• Unstoppable Force - When moving over a creature, obstacle, or structure for the first time in a round you perform the Trample attack as a  free action
• Big Boned - +5 to AC
• Sharpened Marrow - +15 climb speed
• Overwhelming Mass - Moving through creatures same size or smaller creatures does not count as difficult terrain
• You may choose to spend additional Guile when activating this ability. For each additional Guile you spend (up to 3 more(6 total)) you gain +1 AC and +5 more climb speed. (up to +8 AC and 30ft Climb Speed maximum) 

Trample - (attack) can only be performed by the Unstoppable Force benefit. you run over target creatures occupying the same space as you, they take 4d10 bludgeoning damage (magical) ,they must perform a dexterity saving throw (use 8+ proficiency + dexterity modifier) or fall prone, on a successful save they take half damage and do not fall prone. 

Smash - (action) you slam into the ground affecting a 15 ft cube surrounding you creatures within this area must perform a dexterity saving throw or take 3d12 force damage,on a successful save they take half as much. 

Momentum - (Action) after moving in a single direction for at least 20 ft you become an unstoppable force and you may force targets to make saving throw up to 3 structures, obstacles or creatures in your path, and 8+ proficiency + dexterity modifier is your saving throw DC. The attack knocks affected creatures prone and deals 4d12 force damage to the creature, on a successful save the affected creatures take half damage and are not knocked prone. Structures/obstacles automatically fail and take critical damage.