Elusive. The viper doesn't provoke opportunity attacks when it moves out of an enemy's reach.

Venom Proliferation. While the viper is within 5 feet of the target, the target is vulnerable to poison damage. If the target is immune to poison they instead become resistant to it.

Shadow Sap. While the viper is within 5 feet of the target, the target has disadvantage on saving throws against any spell you cast.

Slippery. It can move through other creatures and objects as if they were difficult terrain. The viper takes 5 force damage if it ends its turn inside an object.

Shadow Sap. While the viper is within 5 feet of the target, the target has disadvantage on saving throws against any spell you cast.

Shadow Hunt. At the start of its turn, the viper automatically knows its target’s location. If the target was hidden, it is no longer hidden from the viper.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 5 (2d8 + 4) piercing damage.

Constrict. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 6 (2d6 + 4) bludgeoning damage, and the target is grappled (escape DC 15). Until this grapple ends, the creature is restrained, and the viper can't constrict another target.

The viper can make opportunity attacks, but only against its target.