Hellish Weapons. The erinyes's weapon attacks are magical and deal an extra 13 (3d8) poison damage on a hit (included in the attacks).
Magic Resistance. The erinyes has advantage on saving throws against spells and other magical effects.
Multiattack. The erinyes makes three attacks.
Longsword. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) slashing damage, or 9 (1d10 + 4) slashing damage if used with two hands, plus 13 (3d8) poison damage.
Longbow. Ranged Weapon Attack: +7 to hit, range 150/600 ft., one target. Hit: 7 (1d8 + 3) piercing damage plus 13 (3d8) poison damage, and the target must succeed on a DC 14 Constitution saving throw or be poisoned. The poison lasts until it is removed by the lesser restoration spell or similar magic.
Parry. The erinyes adds 4 to its AC against one melee attack that would hit it. To do so, the erinyes must see the attacker and be wielding a melee weapon.