Blightborn Leviathon

Keen Smell. The Blightborn Leviathan has advantage on Wisdom (Perception) checks that rely on smell.

Undead Fortitude. If damage reduces the Blightborn Leviathan to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the Blightborn Leviathan drops to 1 hit point instead.

Assimilate the Fallen. When the Blightborn Leviathan reduces a living creature to 0 hit points with a melee attack, it can use its smaller arms to assimilate the creature, regaining hit points equal to half the damage dealt by the final blow. The creature starts to be absorbed into the Leviathan's form, becoming a part of its undead mass unless saved by a Remove Curse spell or similar magic before the Leviathan's next turn.

Multiattack. The Blightborn Leviathan makes two attacks with its Slam.

Slam. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 18 (2d10 + 7) bludgeoning damage.

Grasping Arms. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: The target is grappled (escape DC 18). Until this grapple ends, the creature is restrained, and the Blightborn Leviathan can't use Grasping Arms on another target. The Leviathan has two smaller arms and can grapple two targets at a time.

Devour Soul. (Recharge 5–6) The Blightborn Leviathan targets one creature it has grappled. The target must make a DC 18 Constitution saving throw, taking 55 (10d10) necrotic damage on a failed save, or half as much damage on a successful one. If this damage reduces the target to 0 hit points, the target is assimilated as per the Assimilate the Fallen trait.

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