Grappler: The viper Monarch has advantage when grappling and constricting 

Claw: Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 11 (2d12 + 3) slashing damage. 

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 11 (2d8 + 3) piercing damage. The target must also make a dc 17 con save or take 5d8 poison damage, be poisoned, and be paralyzed, fall unconscious, or become incapacitated as long as they have the poison condition which lasts for an hour.

Constrict. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 6 (1d10 + 3) bludgeoning damage, and the target is grappled (escape DC 17), Until this grapple ends, the creature is restrained, and the viper can't constrict another target. The viper's movement speed is zero when constricting.

Crush: The viper must be constricting a creature to take this action. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 28 (5d8 + 3) bludgeoning damage.

Poison spit: The viper spits a 30ft circle of poison every creature within the area must make a dc 17 con save or take 5d8 poison damage, be poisoned, and be paralyzed, fall unconscious, or become incapacitated as long as they have the poison condition which lasts for an hour.

Pull and Constrict: Range 20ft; Target creature make a dc 17 Str check, or be pulled and constricted by the viper.

Hypnotic Gaze: The viper monarch stares at a target and if the target fail a dc 18 WIS save they are charmed by the Viper monarch, The targeted creature rolls with disadvantage if it's grappled by a viper or the viper monarch. This doesn't work if the targeted creatures doesn't rely on sight, or if the viper monarch is blinded

Grapple: The viper monarch can grapple a target as a bonus action.

Pull and Grapple: Range 20ft; Target creature make a dc 17 Str check, or be pulled and grappled by the viper monarch.