Multiattack

The hebi-doku can use its Transfixing Rattle. It then makes two attacks: one with its bite and one with its disabling sting, or two with its toxic spittle.

Bite

Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) piercing plus 14 (4d6) poison damage.

Disabling Sting

Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 12 (3d4 + 5) piercing damage, and the target must succeed on a DC 16 Constitution saving throw or be unable to use bonus actions and reactions until the end of its next turn.

Toxic Spittle

Ranged Weapon Attack: +8 to hit, range 30/90 ft., one target. Hit: 10 (3d6) poison damage, and the target must make a DC 16 Constitution saving throw. On a failure, the target is paralyzed for 1 minute. On a success, the target is poisoned for 1 minute. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Transfixing Rattle

The hebi-doku rattles its tail at one creature it can see within 30 feet of it. The target must make a DC 14 Wisdom saving throw or be incapacitated and have its speed reduced to 0 until the end of its next turn.