Viperblade Enforcer

Evasion. If the Viperblade is subjected to an effect that allows a Dexterity saving throw to take only half damage, it instead takes no damage on a success, and half on a failure.

Poison Mastery. Their weapons are always coated in viper venom. On hit, target must succeed on a DC 15 Constitution saving throw or take 10 (3d6) poison damage and become poisoned for 1 minute. The target may repeat the saving throw at the end of each turn.

Serpentine Reflexes. The Viperblade may take one additional reaction per round, which can be used for opportunity attacks or parries.

Spellcasting. The [monster name] is a #-level spellcaster. Its spellcasting ability is [ability score] (spell save DC #, +# to hit with spell attacks). The [monster name] has following [class name] spells prepared:
Cantrips (at will): [spell name], [spell name]
1st level (# slots): [spell name], [spell name]

Multiattack. The Viperblade makes three melee attacks or two ranged attacks.

Viper Fang (Shortsword, Melee). +8 to hit, reach 5 ft., one target. Hit: 8 (1d6 + 5) piercing plus 7 (2d6) poison damage.

Throwing Knives (Ranged). +7 to hit, range 20/60 ft., one target. Hit: 6 (1d4 + 4) piercing. On hit, target must succeed on a DC 13 Dex save or become marked (attacks from the Viperblade have advantage until end of its next turn).

Shadowstep (Recharge 4–6). The Viperblade teleports up to 30 feet to an unoccupied space in dim light or darkness.

Viper Coil. When a creature within 5 feet misses the Viperblade with a melee attack, it may immediately make one Viper Fang attack against that creature.