Blighted Sea Serpent

Amphibious. The Blighted Sea Serpent can breathe air and water.

Legendary Resistance (2/Day). If the Blighted Sea Serpent fails a saving throw, it can choose to succeed instead.

Siege Monster. The Blighted Sea Serpent deals double damage to objects and structures.

Hive Mind. The Blighted Sea Serpent shares a telepathic link with other Blighted creatures. If one Blighted creature is aware of a hostile creature, all Blighted creatures in the hive mind within range are also aware.

Blighted Scourge. Natural weapon attacks by the Blighted Sea Serpent carry the Blighted Scourge infection. A creature hit by the serpent's attacks must succeed on a DC 18 Constitution saving throw or contract the Blighted Scourge.

Death Burst. When the Blighted Sea Serpent drops to 0 hit points, it releases a violent explosion of blighted energy. Each creature within 30 feet must make a DC 18 Constitution saving throw or take 28 (8d6) blighted energy damage and become infected with the Blighted Scourge. On a successful save, creatures take half damage and are not infected.

Enhanced Blighted Aura. The Blighted Sea Serpent emits a 20-foot radius of corrupting energy. Creatures that start their turn within this aura must make a DC 18 Wisdom saving throw or take 10 (3d6) blighted energy damage and suffer disadvantage on saving throws against Blighted effects until the start of their next turn. Blighted creatures are immune to this effect.

Multiattack. The Blighted Sea Serpent makes one Bite attack and one Constrict or Tail attack.

Bite. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 20 (2d12 + 7) piercing damage plus 10 (3d6) blighted energy damage.

Constrict. Melee Weapon Attack: +12 to hit, reach 20 ft., one creature. Hit: 29 (4d10 + 7) bludgeoning damage, and the target is grappled (escape DC 20). Until this grapple ends, the target is restrained, and the sea serpent can’t constrict another target.

Tail. Melee Weapon Attack: +12 to hit, reach 20 ft., one target. Hit: 18 (2d10 + 7) bludgeoning damage. If the target is a creature, it must succeed on a DC 20 Strength saving throw or be pushed up to 30 feet away and knocked prone.

Blighted Breath (Recharge 5–6). The Blighted Sea Serpent exhales a cloud of corrupted energy in a 60-foot cone. Each creature in that area must make a DC 18 Constitution saving throw, taking 45 (10d8) blighted energy damage on a failed save, or half as much on a successful one. Blighted creatures within the cone regain hit points equal to half the damage dealt.