The necromancer is a 5th-level spellcaster. Spellcasting ability is Intelligence (spell save DC 16, +8 to hit with spell attacks).

1st level (4 slots):
ray of sickness, false life, cause fear

2nd level (3 slots):
blindness/deafness, gentle repose, ray of enfeeblement

3rd level (3 slots):
animate dead, vampiric touch, feign death

4th level (3 slots):

blight, phantasmal killer, Edvards black tentacles

5th level (1 slot):
danse macabre

chill touch, toll the dead, mage hand, minor illusion

Grim Harvest (1/Turn).
When the necromancer kills a creature with a spell of 1st level or higher, it regains HP equal to twice the spell’s level (or three times if the spell was necromancy).

Undead Thralls.
Undead created by the necromancer gain +9 HP and add the necromancer’s proficiency bonus to their weapon damage rolls.

Master of the Grave.
Undead within 30 feet of the necromancer have advantage on saving throws against turning effects.