Cult Leader

Key of Prophesy.  The cult leader can always act in a surprise round, though he is still considered surprised if he has not taken an action.  He receives a +3 bonus to initiative.

Dark Devotion. The cult leader has advantage on saving throws against being charmed or frightened.

Innate Spellcasting. The cult leader's innate spellcasting ability is Wisdom (spell save DC 16).  He can innately cast the following spells, requiring no material components:

2/day each:  detect thoughts, dimension door, haste, slow

1/day each: suggestion, teleport

Spellcasting. The cult leader is a 10th-level spellcaster. Its spellcasting ability is Wisdom (spell save DC 16, +8 to hit with spell attacks). The cult leader has the following cleric spells prepared:

Cantrips (at will): guidance, light, sacred flame, spare the dying, thaumaturgy

1st level (4 slots): cure wounds, identify, guiding bolt

2nd level (3 slots): lesser restoration, silence, spiritual weapon

3rd level (3 slots): dispel magic, mass healing word, spirit guardians

4th level (3 slots): banishment, death ward, guardian of faith

5th level (2 slots): flame strike

Multiattack. The fanatic makes two melee attacks, or one melee attack and cast one cantrip.

Mace. Melee Weapon Attack: +3 to hit, reach 5 ft., one creature. Hit: 3 (1d6) bludgeoning damage.

Esoteric Vengeance. As a reaction when struck by a melee attack, the cult leader can expend a spell slot to do 10 (3d6) necrotic damage to the attacker.  If the cult leader expends a spell slot of 2nd level or higher, the damage increases by 1d6 for each level above 1st.