Coil: The Venomworm can coil into a ball as an action, gaining 4 AC, resistant to any damage that hits with a Dex or Con save, and unable to make any attacks until it uncoils as a bonus action. While Coiled, The venomworm can expend its hit dice to regain health, only able to use the healing portion of this ability once per long rest.

Multi-attack: The Venomworm can make 2 bite attacks 

Bite. melee weapon attack: +7 to hit, reach 15 ft., one target. Hit: 11 (1d8+6) piercing damage and the target must make a DC 15 Constitution saving throw. Target takes 9 (3d6) poison damage on a failed save, are poisoned, and have suffer 1 level of exhaustion until an antivenom is acquired, or half as much damage and no other effects on a successful save.

Needle Storm (Recharges after 6 rounds). The Venomworm spreads its plates around its face and fires poisoned needles in a 45 foot cone from it. Each creature in that area must make a DC16 Dexterity saving throw, taking 12 (4d6) piercing damage, 12 (4d6) poison damage, are poisoned, and suffer 1 level of exhaustion on a failed save or half as much damage and no other effect on a successful save.