Rune Carver. Whenever the rune knight finishes a long rest, it can touch up to 2 objects and inscribe a different rune onto each of the objects. The object must be a weapon, a suit of armor, a shield, a piece of jewelry, or something else that can be worn or held in a hand. The rune remains on an object until the rune knight finishes a long rest, and an object can bear only one runes at a time.

While it has the runes on it's person, the rune knight have darkvision out to a range of 120 feet (included in it's statistics) and has advantage on Wisdom (Insight) checks, and doubles it's proficiency bonus for any ability check it makes that uses it's proficiency with a tool. .

Fire Rune (1/Short or Long Rest). When the rune knight hits a creature with an attack, the target takes an extra (7) 2d6 fire damage, and it must succeed on a DC 15 Strength saving throw or be restrained for 1 minute. While restrained by the shackles, the target takes 7 (2d6) fire damage at the start of each of its turns. The target can repeat the saving throw at the end of each of its turns, banishing the shackles on a success.

Unarmed Fighting. At the start of each of the rune knight's turn, it can deal 1d4 bludgeoning damage to one creature it has grappled. 

Second Wind (1/Short or Long Rest). The rune knight can take one additional action on it's turn.

Multiattack. The rune knight makes two unarmed strikes or javelin attacks.

Unarmed Strike. Melee Weapon Attack: +6 to hit, reach 5 ft., 1 target. Hit: 7 (1d6 + 4) bludgeoning damage, or 8 (1d8 + 4) bludgeoning damage if the rune knight isn't wielding any weapons or a shield. If it's the rune knight's first attack on it's turn while using it's Giant's Might, it deals an additionnal 3 (1d6) damage.

Javelin. Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft. or range 30/120 ft., one target. Hit: 7 (1d6 + 4) piercing damage. If it's the rune knight's first attack on it's turn while using it's Giant's Might, it deals an additionnal 3 (1d6) damage.

Giant Might (2/Long Rest). The rune knight transforms for 1 minute, during which it becomes Large, has advantage on Strength checks and Strength saving throws, and it's first attack on it's turn deal an additional 3 (1d6) damage (included in the attacks).

Second Wind (1/Short or Long Rest). The rune knight regains 10 (1d10 + 5) hit points.

Cloud Rune (1/Short or Long Rest). When a creature the rune knight can see ends it's turn within 30 feet of it, it must succeed on a DC 15 Wisdom saving throw, or be charmed by the rune knight for 1 minute. A creature charmed this way has it's speed reduced to 0 and is incapacitated as it descends in a dreamy stupor. A charmed creature can repeat the saving throw at the end of each of it's turns, ending the effect on a success.