Assassin Bugs

Assassinate. During its first turn, the Assassin Bug has advantage on attack rolls against any creature that hasn't taken a turn. Any hit the assassin scores against a surprised creature is a critical hit.

Evasion. If the Assassin Bug is subjected to an effect that allows it to make a Dexterity saving throw to take only half damage, the Assassin Bug instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Sneak Attack. Once per turn, the Assassin Bug deals an extra 14 (4d6) damage when it hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of the Assassin Bug that isn't incapacitated and the assassin doesn't have disadvantage on the attack roll. 

Hot Under The Collar. The Assassin Bug Lose All Effect of Follow The Blood when Damage by Fire.

Multiattack. The assassin makes two Attacks one with Rustic Dagger & Follow The Blood.

Rustic Dagger. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.

Follow The Blood. The Assassin Bug makes one Grapple attack against a Medium or smaller target it is grappling. If the attack hits, the target is swallowed, and the grapple ends. The swallowed target is blinded and restrained, and it takes 10 (3d6) Necrotic damage at the start of each of the Assassin Bug  turns. The Assassin Bug can have only one target Restraint at a time. If the Assassin Bug dies, a Restraint creature is no longer restrained by it and can escape from the corpse using 5 feet of movement, the Assassin Bug has advantage on strength rolls against any creature that has lost HP. 

Swarm Tactic. All physical attack directed to the Assassin Bug will be Redirected to the player under the effect of Follow the Blood.