Dark Devotion. The fanatic has advantage on saving throws against being charmed or frightened.
Icy Doom. When the cultist dies, its corpse freezes for 9 days, during which time it can't be thawed, harmed by fire, animated, or raised from the dead.
Spellcasting. The fanatic is a 4th-level spellcaster. Its spellcasting ability is Wisdom (spell save DC 11, +3 to hit with spell attacks). The fanatic has the following cleric spells prepared:
Cantrips (at will): light, sacred flame, thaumaturgy
1st level (4 slots): command, inflict wounds, shield of faith
2nd level (3 slots): hold person, spiritual weapon
Multiattack. The fanatic makes two melee attacks.
Dagger. Melee or Ranged Weapon Attack: +4 to hit, reach 5 ft. or range 20/60 ft., one creature. Hit:4 (1d4 + 2) piercing damage.
Fanatics are often part of a cult's leadership, using their charisma and dogma to influence and prey on those of weak will. Most are interested in personal power above all else.