Pact Magic
The soldier is a 1st-level warlock (spell save DC 12, +4 to hit with spell attacks). It has the following warlock spells prepared:
Cantrips (at will): Eldritch Blast, Minor Illusion, Blade Ward
1st Level (2 slots): Armor of Agathys, Hex
Actions
Multiattack. The soldier makes two attacks with its longsword or light crossbow.
Longsword. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 2) slashing damage, or 8 (1d10 + 2) slashing damage if wielded with two hands.
Light Crossbow. Ranged Weapon Attack: +4 to hit, range 80/320 ft., one target. Hit: 6 (1d8 + 2) piercing damage.
Eldritch Blast. Ranged Spell Attack: +4 to hit, range 120 ft., one target. Hit: 6 (1d10 + 2) force damage.
Hex - The soldier places a curse on a creature it can see within 90 feet. Until the spell ends, the target takes an extra 1d6 necrotic damage whenever it is hit by the soldier's attack.