Arban Adler

Touch of Death. Whenever Arban is within 20 feet of an enemy, they have to make a Constitution Saving Throw, DC 15, on a failure, the target's movement speed is reduced to 0, until the beginning of their next turn.

Spellcasting. Arban is an 8th-level spellcaster. His spellcasting ability is INT (DC 15, +7 to hit with spell attacks). Arban has the following spells prepared:
Cantrips (at will): Chill Touch, Mage Hand, Prestidigitation, Thaumaturgy, Thunderclap, Toll the Dead
1st level (6 slots): Catapult, Dissonant Whispers, False Life, Hunter's Mark, Inflict Wounds, True Strike
2nd level (4 slots): Arcane Lock, Cloud of Daggers, Levitate, Shadow Blade
3rd level (3 Slots): Animate Dead, Counterspell, Fly, Pulse Wave
4th level (2 Slots): Dimension Door, Phantasmal Killer, Summon Greater Demon

Sneak Attack.
Once per turn, you can deal an extra 5d6 damage to one creature you hit with an attack if you have advantage on the attack roll. The attack must use a finesse or a ranged weapon.

You don’t need an advantage on the attack roll if another enemy of the target is within 5 feet of it, that enemy isn’t incapacitated, and you don’t have disadvantage on the attack roll.

Dagger. Melee Weapon Attack: +8 to hit, reach 5 ft., 1 target. Hit: (3d4 + 4) Piercing & Cold damage. 

Dagger. Ranged Weapon Attack: +6 to hit, reach 60 ft., 1 target. Hit: (3d4 + 4) Piercing & Cold damage. 

Counterspell. As a reaction, the spell counterspell can be cast.