Chronoknight

A time-twisting Fighter subclass based off the one posted by u/dakila101in r/UnearthedArcana, with some alterations my group thought it could use for balancing.

Chronophantom

3rd-level Chronoknight feature

You've learned a type of time magic that you can use to augment your combat capabilities. Whenever you teleport, you can leave behind a remnant of yourself called a Chronophantom. the Chronophantom appears as a translucent version of yourself and is summoned on the exact spot you left. While it exists, you can see, hear, and speak through it. The phantom is untargetable and is invulnerable to any damage.

The Chronophantom lasts until the end of your next turn or until you teleport again.

Temporal Strike

3rd-level Chronoknight feature

Once on your turn when you reach 3rd level, you can imbue one of your melee attacks with chronomancy. Make the melee attack against a target within 15 feet. On a hit, you deal an additional 1d6 force damage and you immediately teleport to an unoccupied space within 5 feet of the target.

The additional damage increases to 2d6 when you reach 11th level. The distance of the creature you can target also increases as you gain levels in this class: 30 feet at 7th level, and 60 feet at 13th level.

Temporal Bubble

7th-level Chronoknight feature

Your affinity for chronomancy has enabled you to cast the Slow spell up to your proficiency modifier per long rest. When cast this way, the spell creates a 30ft sphere and can affect up to 3 creatures, it does not require concentration. 

Flash Forward

7th-level Chronoknight feature

You can make your attacks originate from the space of your Chronophantom when you take the attack action. When you use Temporal Strike, you can choose not to teleport. Instead, a Chronophantom is summoned in an unoccupied space within 5 feet of your target.

Rewind

10th-level Chronoknight feature

 You can use time magic to back track on your path. As a bonus action, you can teleport to the space of your Chronophantom. Alternatively, as a reaction when you are targeted by an attack or forced to make a Strength, Constitution, or Dexterity saving throw, you can teleport to the space of your Chronophantom. If it is an attack and you are no longer in its range, the attack misses. Otherwise the attack is made with disadvantage. If it is an effect and you are no longer in its range or area of effect, you automatically succeed on the save, otherwise, you have advantage on the saving throw.

Once you use this feature, you cannot do so again until you finish a short or long rest.

Time Winder

15th-level Chronoknight feature

You masterfully integrate your chronomancy with your martial abilities. When you roll initiative, and are not surprised, you can use Temporal Strike once before combat begins. In addition, you gain the following benefits when you use the following Fighter abilities.

Action Surge. You can make an extra Temporal Strike as a free action.

Second Wind. You regain one use of Rewind.

Borrowed Time

18th-level Chronoknight feature

When you take damage that reduces you to zero hit points and you have a Chronophantom available, you can use a reaction to gain temporary hit points equal to the damage taken + your fighter level and teleport to the space of your Chronophantom. While you have these temporary hit points, having 0 hit points doesn’t cause you to become unconscious. You still must make death saving throws, and you suffer the normal effects of taking damage while at 0 hit points. These temporary hit points last until the end of your next turn. If you are still at 0 hit points you fall unconscious.

Once you use this feature, you cannot do so again until you finish a long rest.