Stone Camouflage. The cairn wight has advantage on Dexterity (Stealth) checks made to hide in rocky terrain.

Sunlight Sensitivity.  While in sunlight, the cairn wight has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Multiattack. The cairn wight makes two skull mace attacks or two rock attacks. It can use its Soul Drain in place of one skull mace attack.

Death Grip. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 13 (2d6 + 6) bludgeoning damage, plus 21 (6d6) necrotic damage.  If the target is a creature, it is grappled (escape DC 19). Until this grapple ends, the target is restrained, and the stone giant wight can't use Death Grip on another target. 

In addition, if the target is a creature, it must succeed on a DC 19 Constitution saving throw or suffer 1 level of exhaustion. If the target fails the saving throw by 5 points or more, it suffers an additional level of exhaustion. This exhaustion remains until it is healed magically: a Lesser Restoration will remove one level of the exhaustion, a Greater Restoration  will remove three levels. The target dies if it suffers 6 levels or exhaustion.

A humanoid or giant slain by this attack rises 24 hours later as a shadow under the cairn wight's control, unless the victim is restored to life or its body is destroyed. The cairn wight can have no more than twelve shadows under its control at one time.

Rock. Ranged Weapon Attack: +11 to hit, range 60/240 ft., one target. Hit: 28 (4d10 + 6) bludgeoning damage.

Rock Bowling. The cairn wight send a rock tumbling along the ground in a 60-foot line that is 5 feet wide. Each creature in that line must make a DC 19 Dexterity saving throw, taking 28 (4d10 + 6) bludgeoning damage and falling prone on a failed save, on a success they take no damage and remain standing. 

Kick. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 9 (1d6 + 6) bludgeoning damage. If the target is Medium size or smaller it must make a DC 19 Dexterity saving throw or be flung 30 feet away from the stone giant wight and fall prone.

Skull Mace. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 19 (3d8 + 6) bludgeoning damage, plus 10 (3d6) necrotic damage.

Soul Drain. Melee Weapon Attack: +11 to hit, reach 15 ft., one creature. Hit: 21 (4d6 + 7) necrotic damage. If the target is a creature, it must succeed on a DC 19 Constitution saving throw or suffer 1 level of exhaustion. If the target fails the saving throw by 5 points or more, it suffers an additional level of exhaustion. This exhaustion remains until it is healed magically: a lesser restoration can remove one level of exhaustion from a victim with two or fewer levels, a greater restoration will remove three levels of exhaustion. The target dies if it suffers 6 levels or exhaustion. 

A humanoid or giant slain by this attack rises 24 hours later as a shadow under the cairn wight's control, unless the victim is restored to life or its body is destroyed. The cairn wight can have no more than twelve shadows under its control at one time.

Rock Catching. If a rock or similar object is hurled at the cairn wight, it can, with a successful DC 10 Dexterity saving throw, catch the missile and take no bludgeoning damage from it.

The cairn wight can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The cairn wight regains spent legendary actions at the start of its turn.

Boot. The cairn wight uses Kick.

Club (Costs 2 Actions). The cairn wight makes a skull mace attack.

Death Touch (Costs 2 Actions). The cairn wight uses Soul Drain.

Feat of Athletics. The cairn wight makes a DC 20 Strength (Athletics) check. If it succeeds, it can Climb 20 feet, Jump 20 feet or Dash 40 feet. If it fails, the distance it moves is halved. 

Rend the Veil. The cairn wight momentarily tears the veil between the material plane and the shadowfell, summoning a  shadow under the cairn wight's control. The cairn wight can have no more than twelve shadows under its control at one time.