Bone Colossus

Hive Mind. All elements of the bone colossus within 50 miles of their main body constantly communicate with each other. If one is aware of a particular danger, they all are.

Siege Monster. The bone colossus deals double damage to objects and structures.

Skeleton Aid. If there are skeletons nearby the bone colossus can telepathically command them to form into itself and add up to 10 hp per skeleton (40 hp max) as a bonus action.

Swarm Form. A bone colossus can use its action to disperse into four large versions of itself with each having a fourth of the original bone colossus hit points. Also as an action it may form back into its original form but only if all four versions are adjacent to themselves.

Turn Resistance. The bone colossus has advantage on saving throws against any effect that turns undead.

Dead Weight. If the bone colossus is defeated in its colossus form its body shatters into hundreds of bones, any creature within 15 ft. must make a DC 16 Dexterity saving throw or take 4d6 bludgeoning damage as it is hailed with bones.

Death Defying. When the bone colossus is brought to 0 hit points its essence will be put in a single skull only extinguishable to its master. The skull must then be buried in a cemetery for 24 hours until it regain its form.

Multiattack (Colossus Form Only). The bone colossus makes two thunderous slam attacks, or a shockwave stomp and one thunderous slam if able to do so.

Thunderous Slam (Colossus Form Only). Melee Weapon Attack: +12 to hit, reach 20 ft., one target. Hit: 36 (4d12 + 7) bludgeoning damage plus 10 (3d6) thunder damage, and the target must make a DC 20 Strength saving throw or be knocked prone.

Shockwave Stomp (Recharge 5-6). The bone colossus lifts its leg and stomps the ground with great force, enough to shake the ground. Any creature within a 60 foot radius must make a DC 22 Dexterity saving throw or be knocked prone.

Razor Teeth (Swarm Form Only). Melee Weapon Attack: +12 to hit, reach 5 ft., one creature in the swarm’s space. Hit: 21 (4d6 + 7) piercing damage.

Dispersal (Swarm Form Only). Each swarm separates further into dozens of individual skeletons, which scatter in different directions. Attacking the skeletons is ineffectual; the bone colossus is effectively removed from play while it is dispersed. The bone colossus must spend at least 1 minute fully dispersed before it can reform as an action. After dispersing, it must reform as a single bone colossus within 60 feet of its prior location.