Big Bones

Spooky Disposition. Big Bones is immune to the charmed and frightened condition, and cannot be put to sleep.

Turn Immunity. Big Bones is immune to effects that turn undead.

Skeletal Fragility.  Whenever Big Bones receives bludgeoning damage or a critical hit, he must roll a Constitution saving throw equal to the damage taken.  On a failed save, Big Bones loses some bones, and his Multiattack is reduced by one.

Multiattack. Big Bones makes three unarmed attacks.

Unarmed strike. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 12 (2d6 + 5) bludgeoning damage.

Gotcha now. Big Bones may replace one of his unarmed attacks with a grapple or shove attack.  Melee Grapple: +5 to hit, reach 10 ft., one target. Contested athletics/acrobatics with target.  Creatures one or more sizes smaller than Big Bones have disadvantage on this roll.

Gather dem bones. As a bonus action, Big Bones can collect some of his lost bones.  Big Bones restores enough bones to reduce any Multiattack penalty from Skeletal Fragility by one.