Boiúna

Gargantuan beast (titan), lawful evil

Armor Class 19 (natural armor)
Hit Points 465 (30d20+150)
Speed 30 ft., swim 100 ft.

STR	DEX	CON	INT	WIS	CHA
30 (+10)	22 (+6)	20 (+5)	18 (+4)	22 (+6)	26 (+8)

Condition Immunities charmed, grappled, restrained
Skills Athletics +17, Deception +16, Perception +13
Senses darkvision 60 ft., passive Perception 23
Languages Aquan, Common
Challenge 22 (41,000 XP)

SPECIAL TRAITS

• Amphibious. The boiúna breathes air and water.
• Serpentiginous Rebirth. A creature slain by the boiúna is reincarnated 24 hours later as an ordinary river snake with no recollection of their former life. Their former body (but not their gear) dissolves into mud. Once they are reincarnated, they cannot be returned to life by raise dead or resurrection, though reincarnate or wish can bring them back in their original form even if their body is not present by simply touching the body of water where they were slain, or the body of the boiúna, or the snake they became when reborn.
• Siege Monster. The boiuna deals double damage to objects and structures.
• Steal Shadow. A creature that ends its turn adjacent to the boiúna must succeed a DC 23 Charisma saving throw or have its shadow stolen from it. Starting on its next turn, and every hour thereafter, a creature that has its shadow stolen must succeed a DC 23 Constitution saving throw or gain 1 level of exhaustion. If the boiúna is killed or if remove curse is cast on a creature whose shadow has been stolen, its shadow returns and they no longer need to save against gaining levels of exhaustion, but any exhaustion already accrued remains. The boiúna can suppress or regain use of this ability as a bonus action.
• Stench. The awful reek of the boiúna causes non-reptilian creatures within 60 feet to become poisoned unless they succeed on a DC 20 Constitution saving throw. They remain poisoned until they complete a short rest. A successful save grants immunity to the boiúna’s stench for 24 hours.
• Unstoppable. The boiúna’s movement is never impeded by difficult terrain.

ACTIONS

• Multiattack. The boiúna makes one bite attack and one tail attack.
• Bite. Melee Weapon Attack: +17 to hit, 60 ft. reach, all targets in a 10-foot square. Hit: 75 (10d12 + 10) piercing damage. If the boiúna bites a single Large or smaller creature, the target must succeed on a DC 25 Dexterity or Strength saving throw (target’s choice) or be swallowed by the boiúna. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the boiúna, and it takes 10 (3d6) acid damage and 21 (6d6) bludgeoning damage at the start of each of the boiúna’s turns. If the boiúna dies, a swallowed creature is no longer restrained and can escape from the corpse by using 30 feet of movement, exiting prone.
• Tail. Melee Weapon Attack: +17 to hit, 60 ft. reach, all targets in a 20-foot line, 5 feet wide. Hit: 48 (14d10 + 10) bludgeoning damage and targets must succeed on a DC 25 Strength or Dexterity saving throw (target’s choice) or be pushed 10 feet in a direction chosen by the boiúna.
• Change Shape. The boiúna can transform into a Small or Medium humanoid or back into its original form. In this humanoid form, it loses its bite and tail attacks.
• Enchanting Gaze. A boiúna can attempt to charm a creature within 120 feet of it with its gaze. The creature must succeed a DC 23 Wisdom saving throw or be charmed for 1 minute.
• Immobilize Ship. The boiúna can turn the power of its gaze on a ship within 120 feet, causing it to halt as if stuck fast on a sandbar or anchor. If the ship has a pilot or captain, they can attempt a DC 23 Wisdom saving throw to resist this effect. On a success, their ship is immune to this effect for 24 hours. If failed, the ship cannot move for 1 hour unless the boiúna releases it. Casting remove curse on the ship grants the pilot or captain a new saving throw with advantage to end the effect.

ABOUT

This titanic serpent has scales of midnight black above and lighter gray below, glistening with water as it haunts the deepest and widest lakes and rivers. Its massive eyes glow like orange bonfires, and their lambent glow can mesmerize creatures who look upon them with the overwhelming presence of the boiúna. Its onyx scales absorb shadows the living shadows of creatures nearby, sapping their vital energy and causing them to waste and die within days. These titanic beasts keep can grow hundreds of feet long and their bodies may span 20 to 30 feet across. They keep to the deepest freshwater they can find. In dry seasons when lakes and rivers become shallow or dry up, they may gouge new channels with their massive bodies or simply slither through the plains and forests to find a new home. They may dig immense holes underwater to find hidden springs or ensure it has a sufficient water supply.

River Kings. Belying its monstrous size and appearance, the boiúna is a highly intelligent creature, even gregarious when properly approached by shamans or others performing the proper rites or seances. They occasionally don human guise, often appearing as wealthy nobles or merchants, and attend parties and dances as they mingle with mortal. Some keep a hordes of smaller snakes in and around their riverine homes in a serpentine semblance of the kingdoms they visit on land.