Actions

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.   Variant: Rope of Entanglement
Some erinyes carry a rope of entanglement (detailed in the Dungeon Master's Guide). When such an erinyes uses its Multiattack, the erinyes can use the rope in place of two of the attacks.

Reactions

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.