Large undead (beast)
Hit Dice: 6d10 (33 hp); saves as a fighter. Immune to poison and disease, resistant to cold, vulnerable to fire.
Armor Class: High (unfeeling flesh + high dexterity)
Movement: As a normal, unencumbered human. A necromanticore can use their move action to leap 30 feet long or 15 feet high.
Demeanor: Arrogant, intelligent, and cruel.
Attack:

• Claws +8 (2d8 damage, if doubles are rolled, the target is pinned to the ground) OR
• Bite +6 (2d4 damage; against pinned targets, the necromanticore has advantage on the attack roll) OR
• Tail Stinger +6 (10 ft. reach, 1d6 damage and target must succeed a Constitution saving throw or become paralyzed with excruciating pain. Every round, the target must make another Constitution saving throw; on a success, they shake off the effects of the venom, but take another 1d6 damage on a failure.)

Special:

• Devour Souls: Whenever a necromanticore slays a living creature, it absorbs their spiritual essence, gaining a number of hit points equal to the slain creature’s hit dice. A creature whose soul has been devoured cannot be revived until the necromanticore has been slain (but it could be reanimated).
• Spellcasting: As an action, the necromanticore can sacrifice 1d6 hit points to cast one of the following spells:
  • Black Breath – The necromanticore exhales a 20-foot-radius cloud of dark vapor that lasts for a number of rounds equal to the hit points spent to cast it. A living creature that enters the cloud must succeed a Charisma saving throw or be sapped of their will to live, suffering disadvantage on all rolls. Once they leave the cloud, they can attempt the saving throw again.
  • Dead Can Dance – The necromanticore can reanimate a number of corpses or skeletons equal to the hit points spent to cast the spell. These creatures are mindless servants obedient only to the necromanticore that created them. If the necromanticore is slain, they immediately revert back to being inanimate.
  • Dolorous Demand – The necromanticore issues a command to a creature it can see within 30 feet. The command can contain a number of words equal to the hit points spent to cast it. The target can choose to resist the spell, but will suffer 2d6 damage as blood trickles from their ears and nose.
  • Ghostflame – Eerie blue flames erupt from the ground to a height of 10 feet, creating a wall with a length of 10 feet per hit point spent to cast it. Ghostflame burns cold, dealing 1d10 damage to living creatures who touch it, even those who are protected from fire. Undead creatures are not harmed. This spell lasts for up to 1 minute, or can be dismissed by the necromanticore. It also ends immediately when the necromanticore is slain.
  • Spectral Flight – The necromanticore disappears into the spectral realm for up to a number rounds equal to the hit points spent to cast the spell. The necromanticore can attempt to pull a creature along with it, but the target can resist it with a successful Strength saving throw.

A terrible foe armed with bestial strength and profane magic.