Cursed Marksman

Magic resistance  The marksman has advantage on saving throws from spells and other magical effects. 

Sharpshooter  The marksman's ranged weapon attacks ignore half and three-quarters cover. Before the marksman makes a ranged attack it can choose to take a -5 penalty to the attack roll. If that attack hits, add +10 to the attack's damage.

Adaptive form: As a bonus action the marksman can grow new limbs or modify existing ones to suit its needs, it can grow wings, fins, gills or other adaptations to navigate its environment, additionally if its form would be altered by magic it such as polymorph, it may use its action to end the effect on itself.

Multiattack. The marksman can make four ranged attacks with its arm bows or one attack with its arms and one attack with its stinger. 

Unarmed strike +12 to hit, 5 ft., 1 target. Hit:  (2d6+ 3) slashing damage. 

Barbed Stinger +12 to hit, 10 ft, 1 target. Hit: (2d6+3) piercing damage the target must make a DC 18 Constitution saving throw, taking (5d10) poison damage on a failed save, or half as much damage on a successful one, on a failed save a target is also paralyzed, a target can repeat its constitution saving throw at the end of each of its turns ending the effect on a success. 

Action Ranged Attack. Arm bow Attack: +12 to hit, range 600 ft., 1 target. Hit: (2d8+ 6) piercing damage and (2d8) force damage 

Adaptive form  As a bonus action the marksman can grow new limbs or modify existing ones to suit its needs, it can grow wings, fins, gills or other adaptations to navigate its environment

Imbue weapons As a bonus action the marksman can imbue one of its arm bows with an effect that takes effect the next time that bow lands an attack, the marksman can choose from one of the following options and may not use the same option twice in a row:

Poison: On a successful hit the target must make a DC 18 Constitution saving throw or take 5d6 poison damage on a failed save or half as much on a successful one, on a failed save the target is also poisoned. 

Burst: On a successful hit the target and any creature within 15 ft must make a DC 18 dexterity saving throw or take 4d10 force damage or half as much on a successful save. 

Pinning: On a successful hit the target must make a DC 18 strength saving throw or have its movement speed reduced to 0 until the end of the marksman's next turn. 

Piercing: On a successful hit the target and anything within a 30 ft line must make a DC 18 dexterity saving throw or take 4d6 force damage, this damage goes through structures and objects, damaging them as well.