Bone Golem

False Appearance. While the golem remains motionless, it is indistinguishable from a pile of bones or ordinary, inanimate skeleton.

Necrotic Absorption. Whenever the Bone Golem is subjected to necrotic damage, it takes no damage and instead regains a number of hp equal to the necrotic damage dealt.

Multiattack. The golem first attacks with its claws, then either its bone club.

Claw. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) slashing damage.

Bone Club. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) bludgeoning damage plus 7 (2d6) necrotic damage.

Bone Prison. When it receives damage, the bone golem can react by throwing some of its bones at the attacker, so long as the attacker is within 30 feet. These bones magically duplicate and form a cage surrounding struck creatures, restraining them. Each round, the imprisoned creature must make a Strength check or remain restrained. If the check fails, the target is still restrained but takes no damage. The target can break out of the bones by dealing 15 points of damage to the prison, which has the same AC as the bone golem itself. Damage to the prison has no effect on the golem. The golem can only have one bone prison active at a time. If it wishes to create a second one, it (or some other creature) must first destroy the existing one.