Bog Tyrant (spinosaurus)

Spinosaurus is an enormous predatory dinosaur that lives in swamps and terrorizes all other creatures in its territory. Even though it prefers to eat fish there are few creatures it won’t try to devour whole. A Bog Tyrant is a half-black dragon spinosaurus that has mutated into a gargantuan monstrosity.

Black dragonborn and some tribes of lizardfolk have been known to sometimes use “trained” bog tyrants as war monsters, equipping them with howdahs and siege weapons.

Howdah. The bog tyrant carries a compact fort on its back. Up to eight Medium creatures can ride in the fort without squeezing. To make a melee attack against a target within 5 feet of the bog tyrant, they must use spears or weapons with reach. Creatures in the fort have three-quarters cover against attacks and effects from outside it. If the bog tyrant dies, creatures in the fort are placed in unoccupied spaces within 5 feet of the bog tyrant.

The howdah is often equipped with a ballista, a mangonel or multiple cannons:

Before the ballista can be fired, it must be loaded and aimed by the howdah’s riders. It takes one action to load the weapon, one action to aim it, and one action to fire it.

Ballista (Riders Only). Ranged Weapon Attack: +6 to hit, range 120/480 ft., one target. Hit: 16 (3d10) piercing damage.

Before the mangonel can be fired, it must be loaded and aimed by the howdah’s riders. It takes two actions to load the weapon, two actions to aim it, and one action to fire it.

Mangonel (Riders Only). Ranged Weapon Attack: +5 to hit, range 200/800 ft. (can’t hit targets within 60 feet of it), one target. Hit: 27 (5d10) bludgeoning damage.

Before the cannons can be fired, each cannon must be loaded and aimed by the howdah’s riders. It takes one action each to load a cannon, one action each to aim a cannon, and one action each to fire a cannon.

Cannon (Riders Only). Ranged Weapon Attack: +6 to hit, range 600/2,400 ft., one target. Hit: 44 (8d10) bludgeoning damage.

Just like black dragons, bog tyrants dwell in swamps lairing in a dismal cave or grotto that is at least partially flooded, providing pools where the bog tyrant rests. The lair is littered with the acid-pitted bones of previous victims. Centipedes, scorpions, and snakes infest the lair, which is filled with the stench of death and decay.

Lair Actions

On initiative count 20 (losing initiative ties), the bog tyrant takes a lair action to cause one of the following effects; the bog tyrant can’t use the same effect two rounds in a row:

• Pools of water that the bog tyrant can see within 120 feet of it surge outward in a grasping tide. Any creature on the ground within 20 feet of such a pool must succeed on a DC 15 Strength saving throw or be pulled up to 20 feet into the water and knocked prone.
• A cloud of swarming insects fills a 20-foot-radius sphere centered on a point the bog tyrant chooses within 120 feet of it. The cloud spreads around corners and remains until the bog tyrant dismisses it as an action, uses this lair action again, or dies. The cloud is lightly obscured. Any creature in the cloud when it appears must make on a DC 15 Constitution saving throw, taking 10 (3d6) piercing damage on a failed save, or half as much damage on a successful one. A creature that ends its turn in the cloud takes 10 (3d6) piercing damage.
• Magical darkness spreads from a point the bog tyrant chooses within 60 feet of it, filling a 15-foot-radius sphere until the bog tyrant dismisses it as an action, uses this lair action again, or dies. The darkness spreads around corners. A creature with darkvision can’t see through this darkness, and nonmagical light can’t illuminate it. If any of the effect’s area overlaps with an area of light created by a spell of 2nd level or lower, the spell that created the light is dispelled.

Regional Effects

The region containing a legendary bog tyrant’s lair is warped by draconic magic, which creates one or more of the following effects:

• The land within 6 miles of the lair takes twice as long as normal to traverse, since the plants grow thick and twisted, and the swamps are thick with reeking mud.
• Fog lightly obscures the land within 6 miles of the lair.

If the bog tyrant dies, vegetation remains as it has grown, but other effects fade over 1d10 days.