Cult Leader of the Great Wurm

Innate Spellcasting. The cultist's innate Spellcasting ability is Charisma (spell save DC 15). It can innately cast the following spells, requiring no material components:

At Will: False Life, Levitate (self only), Mage Armor (self only), Speak With Dead

Spellcasting. The cultist is a 10th-level spellcaster. Its spellcasting ability is Charsima (spell save DC 15, +7 to hit with spell attacks). The cultist has the following warlock spells prepared:

Cantrips (At Will): Chill Touch (2d8), Eldritch Blast (2 beams, + 4 to damage), Infestation (2d6), Prestidigitation

1st - 5th Level (2 5th-level slots): Arms of Hadar, Blight, Crown of Madness, Contact Other Plane, Dimension Door, Hex, Hold Monster, Hunger of Hadar, Mirror Image, Vampiric Touch, 

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

Zealous Resistance (1/Day). When the cult leader fails a saving throw, it can choose to succeed instead.

Ritual Dagger. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) piercing damage.

Conjure Wurms (Recharge 5-6). The cult leader summons 1d4 + 1 swarms of insects which appear within 60 feet of it. The swarms go immediately after the cult leader in the initiative order, remaining for 10 minutes until they are either destroyed or the cult leader uses a bonus action to dismiss them.

Spawn of the Wurm. Ranged Spell Attack: +7 to hit, range 20/60 ft., one target. Hit: A parasitic leech attaches itself to the target. The leech is a tiny beast with AC 6, 1 hit point, a 2 (-4) in every ability score, and a speed of 1 foot. At the start of the target's turn, the leech deals 2 (1d4) points of necrotic damage to it, and the cult leader regains hit points equal to the necrotic damage dealt. The leech remains on the target for 1 minute unless it is killed or scrapped off using an action.

Hunger of the Wurm. When the cultist reduces a creature to 0 hit points, it can use its reaction to consume the creature's life essence, gaining 10 (3d6) temporary hit points.

The cult leader can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The cult leader regains spent legendary actions at the start of its turn.

Move. The cult leader moves up to its speed.

Cantrip. The cult leader casts a cantrip.

Conjure Wurms (Costs 2 Actions). The cult leader recharges and uses Conjure Wurms.