Can't Swim.
Angelic Venom. When the sin eater bites, their attack deals an extra 4d8 Acid damage (included in the attack).
Magic Resistance. The sin eater has advantage on saving throws against spells and other magical effects.
Hunger for sin. A Divine plague that revealed the biting maws. The celestial mistook it as a way to destroy sin. They realized their mistake when the infected's eyes rotted away, but by then they were outnumbered 100 to 1.

Actions

Multiattack. The sin eater makes two melee attacks.
Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 1d6+4 piercing + 18 4d8 Acid damage.
Paralytic Scream. Target creature within 120 ft of the sin eater must succeed on a DC 15 Wisdom saving throw or become paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns. On a successful save, the effect ends and the creature becomes immune to the Sin Eater’s Paralytic Scream for 1 minute.

Varient: God Eater
Can Swim, Huge, HP: 500, AC: 8(20 in flight), Speed Fly: 180ft
Punch. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 18 (4d8) Blunt + 18 (4d8) Radiant
Grab. Grapple. +15 STR against targets str/dex. 7 (2d6) Blunt damage.
Bite. Melee Weapon Attack: +20 to hit, Only targets grappled creatures. Hit: Insta kills the target.