Colossal Skeleton

Turn Immunity. The Colossal Skeleton is immune to effects that turn undead. 

Animated Bones. When the Colossal Skeleton takes more than 40 damage in a single turn, the bones smashed by the damage animate into 2d6 skeletons.

Multiattack. The colossal skeleton can make three attacks per turn, two with its bone maul and one with grasping reach. The skeleton can replace its grasping reach with a throw.

Bone Maul. Melee Weapon Attack: +14 to hit, reach 15 ft., 1 target. Hit: 21 (2d12 + 8) [bludgeoning] damage.

Grasping Reach. Melee Weapon Attack: +14 to hit, reach 15 ft., 1 target. Hit: 17 (2d8 + 8) [bludgeoning] damage. The target must make a DC 19 Dexterity saving throw or become grappled by the Colossal Skeleton. 

Throw. The Colossal Skeleton throws 1 target it has grappled with grasping reach and can throw them up to 60 feet away. The target takes 2d6 [bludgeoning] damage for every 10 feet it is flung. 

Wail (Recharge 5-6). The Colossal Skeleton emits a piercing wail. Every undead within 60 feet of it also starts to wail. Each target within 30 feet of a wailing undead must succeed a DC 18 Wisdom saving throw or take 12d10 [physic] damage or half as much on a successful save. 

The Colossal Skeleton 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 Colossal Skeleton regains spent legendary actions at the start of its turn.

Bone Maul (1 Action). The Colossal Skeleton makes a bone maul attack. 

Throw (1 Action). The Colossal Skeleton makes a throw attack. 

Raise Undead (2 Actions). The Colossal Skeleton raises either 2d6 zombies or 2d6 skeletons to aid it.