Chain golem

Tangled chain body. Each space within a 15ft radius of the golem counts as rough terrain. 

Sure footed. The golem ignores rough terrain and counts it as normal terrain. 

Berserk. Whenever the golem starts its turn with 60 hit points or fewer, roll a d6. On a 6, the golem goes berserk. On each of its turns while berserk, the golem attacks the nearest creature it can see. If no creature is near enough to move to and attack, the golem attacks an object, with preference for an object smaller than itself. Once the golem goes berserk, it continues to do so until it is destroyed or regains all its hit points.

Immutable Form. The golem is immune to any spell or effect that would alter its form.

Magic Resistance. The golem has advantage on saving throws against spells and other magical effects.

Magic Weapons. The golem’s weapon attacks are magical.

Multi attack. The chain golem makes 2 attacks with its chains 

Chains. Melee Weapon Attack: +11 to hit, reach 15 ft., 1 target. Hit: 21 (4d8 + 7) [bludgeoning] damage and the target is grappled (dc 17) to escape but the golem can have 1 grappled target at a time but can make attacks against other creatures still.