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

Abominable Form. Roll a d20 every time the cultist uses its breath weapon: on a 1-10 the cultist is also damaged by the attack. 

Multiattack. The abominable cultists makes an attack with its Fire Breath and then makes two melee attacks: one with its bite and one with its claws.

Claws; Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 6 (1d8 + 2) slashing damage.

Bite; Melee Weapon Attack: +4 to hit, reach 10 ft., one creature. Hit: 7 (1d10 + 2) piercing damage.

Fire Breath (Recharge 5–6). The veteran exhales fire in a 15-foot cone. Each creature in that area must make a DC 15 Dexterity saving throw, taking 10 (3d6) fire damage on a failed save, or half as much damage on a successful one.