b'Siege Dragon Engine \n'b'  Gargantuan   construct ,  neutral evil  \n'b'  Armor Class  18 (natural armor)  Hit Points  390 (20d20 + 180)  Speed  50 ft., climb 50 ft.\n'b' STATS STR: 30 (+10) DEX:  12 (+1)  CON:  28 (+9)  INT:  9 (-1)  WIS:  20 (+5)  CHA:  26 (+8)  \n'b'\n'b'\n'b'\n'b'\n'b'\n'b'\n'b'  Damage Immunities  poison; bludgeoning, piercing, and slashing from nonmagical attacks that aren\xe2\x80\x99t adamantine  Condition Immunities   charmed ,  exhaustion ,  frightened ,  grappled ,  paralyzed ,  petrified ,  poisoned   Senses  blindsight 60 ft.,  darkvision  120 ft., passive  Perception  15  Languages  understands telepathic commands but can\xe2\x80\x99t speak  Challenge  22 (41,000 XP) \n'b' SPECIAL TRAITS \n'b'\n'b'  Battlements . Maggots and grylluses fight from the narrow battlements on the siege dragon engine\xe2\x80\x99s back, mostly behind arrow slits and other forms of  cover  that render attacking them directly ineffective until the engine is reduced to  0 hit points  and destroyed. At that point, most of the fortifications collapse and any remaining uses of the engine\xe2\x80\x99s Deploy Troops action determine what creatures remain on the dragon\xe2\x80\x99s back; these survivors have only half  cover  atop the engine\xe2\x80\x99s ruins. \n'b'  Immutable Form . The siege dragon engine is immune to any spell or effect that would alter its form. \n'b'  Legendary Resistance (3/day) . If the engine fails a saving throw, it can choose to succeed instead. \n'b'  Magic Resistance . The engine has advantage on saving throws against spells and other magical effects. \n'b'  Magic Weapons . The engine\xe2\x80\x99s weapon attacks are magical. \n'b'  Siege Monster . The engine deals double damage to objects. \n'b'\n'b' ACTIONS \n'b'\n'b'  Multiattack . The siege dragon engine makes three attacks: one bite  attack  and two claw attacks. \n'b'  Bite .  Melee Weapon Attack : +10 to hit, reach 20 ft., one target.  Hit : 29 (3d12 + 10) bludgeoning damage. \n'b'  Claw .  Melee Weapon Attack : +10 to hit, reach 10 ft., one target.  Hit : 23 (3d8 + 10) slashing damage and the target must succeed on a DC 18  Strength  saving throw or be knocked  prone . \n'b'  Tail .  Melee Weapon Attack : +10 to hit, reach 20 ft., one target.  Hit : 20 (3d6 + 10) bludgeoning damage. \n'b'  Deploy Troops (3/day) . The engine kneels, depositing one shining gryllus and two simpering maggots (page 209) at an unoccupied location within 20 feet. Roll  initiative  (+0 modifier) for the group, which has its own turns. \n'b'  Poison Breath (Recharge 6) . The engine exhales poison gas in a 120-foot cone. Each creature in that area must make a DC 25  Constitution  saving throw, taking 66 (19d6) poison damage on a failed save, or half as much damage on a successful one. \n'b'  Trample . The engine moves up to its speed. It can move through the spaces of Huge and smaller creatures. It can make one claw  attack  against each creature whose space it enters during this movement. It cannot  attack  a particular creature more than once during this movement. \n'b'\n'b' LEGENDARY ACTIONS \n'b' The siege dragon engine 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\xe2\x80\x99s turn. The engine regains spent legendary actions at the start of its turn. \n'b'\n'b'  Ballista Barrage . The engine\xe2\x80\x99s crew fire mast-sized bolts upon all enemies in a 20-foot-radius sphere centered on a point the engine can see within 120 feet. Each creature in that area must make a DC 16  Dexterity  saving throw, taking 16 (3d10) piercing damage on a failed save, or half as much damage on a successful one. \n'b'  Bark Volley . Gryllus crew bark at all creatures in a 10-footradius sphere centered on a point the engine can see within 120 feet. Each creature in the area must succeed on a DC 16  Strength  saving throw or take 14 (4d6) thunder damage and be knocked  prone . \n'b'  Cage Drop . The engine\xe2\x80\x99s crew drop iron cages on up to two Medium or smaller creatures within 10 feet of the engine. Each creature must succeed on a DC 16  Dexterity  saving throw or be  restrained  by the cage until the cage is opened or lifted. A creature can lift the cage with a successful DC 16  Strength  ( Athletics ) check as an action. The cage\xe2\x80\x99s lock can be opened as an action with a successful DC 16  Dexterity  (thieves\xe2\x80\x99 tools) check. The cage door can be attacked and destroyed (AC 19, 18  hp , immunity to poison and psychic damage,  resistance  to acid damage). \n'b'  Tail Attack . The engine makes a tail  attack . \n'b'\n'b' ABOUT \n'b' The Underhell understands that any world it invades is likely to attempt the foolish act of defending itself. In order to both break the ranks of its enemies and also minimize their own losses, the Fiend Lords created siege engine dragons. These dragons are golems built from the collected corpses of dragons slain by the forces of the Underhell. These creatures are stripped of any free will and forced to serve the Underhell directly. Once the Underhell has forged these creatures, they provide the foundation for semi-living fortresses. \n'b'  Mobile Fortresses . The minions of the Underhell build simple battlements, towers, and walls on the backs of dragon engines, allowing these same minions to travel securely across a battlefield. From their defensive position, the forces are able to strike against their enemies with ease. These constant attacks from these forces are already a serious threat, and defending against the Underhell becomes all but an impossibility once an engine attacks directly. \n'b' This large, wingless, gray dragon has battlements and siege weapons bristling across its back. Dozens of little fiends crawl about up there, aiming the weapons and taking defensive positions among the battlements.'