Ekengarik

All fiendish formians within 1 mile of Ekengarik can telepathically communicate with each other and Ekengarik.

Ekengarik regenerates 10 hit points at the start of her turn, unless she took radiant damage in the last round.

Ekengarik makes three Bite attacks. She can replace one of the attacks with an Acid Spray (if available) attack or a use of Spellcasting.

Melee Attack Roll: +11 to hit, reach 5 ft., one target. Hit: 15 (2d8 + 6) piercing damage and the target must make a DC 19 Constitution saving throw. On a failed save, the target's Strength score is reduced by 2 (1d4). The target dies if this reduces its Strength to 0. Otherwise, the reduction lasts until the target finishes a short or long rest.

Ekengarik spits acid at one creature within 60 feet of her, or two creatures within 60 feet of her and 5 feet of each other. Targets must make a DC 18 Dexterity saving throw, taking 33 (6d10) acid damage on a failed saving throw, or half as much on a successful one.

When hit with an attack, Ekengarik temporarily hardens her carapace, reducing her speed to 0 and increasing her AC by 5 until the start of her next turn.

Ekengarik casts one of the following spells, requiring no material components and using Charisma as the spellcasting ability (spell save DC 18):

At will: Detect Magic, Dispel Magic, Heroism, Magic Missile

1 each/day: Evard's Black Tentacles, Cone of Cold, Confusion, Dimension Door, Geas, Invisibility, Prismatic Wall, Slow