Bone Colossus (Necrotech)

Standing over thirty feet tall, this undead titan is composed of thousands of tiny chittering skeletons, knitted together into one enormous creature of bones and skulls by foul necromantic magic. As the towering colossus strides forward, the earth shakes beneath its feet.

Necrotech Titans. Over sixty years ago, Sandor Greyskin, Master of the Necrophagi, created the first bone collective (see Tome of Beasts) in his laboratory in Darakhan, White City of the Ghouls. Fifty years later, the forbidden lore shared by the vampires has allowed the Necrophagi to develop a new, far larger type of bone collective.

Weapons of War. In his tome of deranged ramblings, Tomislav the Thrice-Flayed theorized how “posthumes”—the tiny skeletal creatures used to make up the bone collectives—might be gathered in even greater numbers to form bigger, stronger creatures. Magenthus Quickborn, current Master of the Necrophagi and a bone collective himself, set to work creating a bone colossus, an undead creature big and powerful enough to serve as a rallying point for the ghoul legions in battle. The first bone colossus was deployed in anger against the Electoral Kingdom of Krakova where it proved decisive in bringing the siege of Wallenbirg to a rapid and favorable conclusion for the undead armies. More bone colossuses are under construction; an enthusiastic Emperor Nicoforus intends to position the huge creatures at the vanguard of each of his imperial legions.

Bone Colossus

Gargantuan undead, chaotic evil
Armor Class 16 (natural armor)
Hit Points 247 (15d20 + 90)
Speed 30 ft.

Saving Throws Con +11, Wis +8
Skills Intimidation +10, Perception +8
Damage Resistances bludgeoning, piercing, and slashing from nonmagical weapons
Damage Immunities necrotic, poison
Condition Immunities charmed, exhaustion, frightened, paralyzed, poisoned
Senses darkvision 120 ft., passive Perception 18
Languages Common, Darakhul
Challenge 14 (11,500 XP)

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. Any bone colossus with at least 40 hit points forms a hive mind, giving it an Intelligence of 14. Below this hit point threshold, it becomes mindless (Intelligence 0). At 0 hp, a few surviving sets of bones scatter, and the Necrophagi must spend months creating a new bone colossus.

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

Swarm Form. A bone colossus can use its action to split into four individual swarms of tiny bone posthumes. Each swarm is Large, has one quarter of the colossus’s current hit points, and attacks and moves independently. A bone swarm can occupy another creature’s space and vice versa, and the swarm can move through openings at least 1 foot wide. As an action, the swarms can reform into a single bone colossus as long as they are adjacent to one another.

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

Actions

Multiattack (Colossus Form Only). The bone colossus makes two thunderous slam attacks.

Thunderous Slam (Colossus Form Only). Melee Weapon Attack: +12 to hit, reach 20 ft., one target. Hit: 29 (4d10 + 7) bludgeoning damage plus 10 (3d6) thunder damage, and the target must make a DC 18 Strength saving throw or be knocked prone.

Razor Teeth (Swarm Form Only). Melee Weapon Attack: +12 to hit, reach 0 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 posthumes, which scatter in different directions. Attacking the posthumes 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.