Magic Resistance. The helmed horror has advantage on saving throws against spells and other magical effects.
Spell Immunity. The helmed horror is immune to burning hands, fireball, and scorching ray.
Multiattack. The helmed horror makes two longsword attacks.
Flaming Longsword. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit:8 (1d8 + 4) fire damage, or 9 (1d10 + 4) fire damage if used with two hands.
Conjure Sword. As a bonus action on its first turn in combat, the helmed horror conjures a longsword-sized blade of fire, which appears in its free hand. This sword disappears in a cloud of smoke when the helmed horror drops to 0 hit points.