Abel Walker

Heartless Mind. Abel is immune to any effect that would read its thoughts, determine whether it is lying, or magically influence its emotions.

Innate Spellcasting. Abel's spellcasting ability is Intelligence (spell save DC 19, +11 to hit with spell attacks). He can innately cast the following spells, requiring no material components:
At will: Mage Hand, Mind Sliver, Minor Illusion, Vicious Mockery, Shield, Animate Objects, Strings Childplay3/day each: Counterspell, Fear, Hypnotic Pattern, Slow, Binding Lines2/day each: Dominate Person (also transform the target on a puppet), Synaptic Static, Wall of Force, Puppet Conversion1/day each: Disintegrate, Feeblemind, Polymorph (into a Living Doll), Conjure Harm Puppet

String Cut. Ranged Spell Attack (Recharge 4-6): +11 to hit, range 60 ft., one target. Hit 15 (3d6+6) slashing damage.

String Impact. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) bludgeoning damage. The attack is magical. Once per turn, when Abel hits a Large or smaller creature with this attack, the target must succeed on a DC 16 Strength saving throw or be pushed up to 15 feet away and knocked prone.

The monster can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The monster regains spent legendary actions at the start of its turn.

Legendary Resistance (3/day). If the Abel fails a saving throw, it can choose to succeed instead.

Forced Conversion. Abel violently tightens his spectral strings and unleashes by casting Puppet Conversion outside his turn.