Multiattack

The ouroban makes three attacks with its greatsword.

Greatsword

Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage plus 3 (1d6) fire damage.

Heavy Crossbow

Ranged Weapon Attack: +5 to hit, range 100/400 ft., one target. Hit: 9 (1d10 + 4) piercing damage.

Fire Breath (Recharge after a Short or Long Rest)

The ouroban exhales fire in a 15-foot cone. Each creature in that area must make a DC 13 Constitution saving throw, taking 14 (4d6) fire damage on a failed save, or half as much damage on a successful one.

Abyssal Fires (Recharges after a Short or Long Rest)

The ouroban summons green flames under up to five creatures within 30 feet of it. Each target must succeed on a DC 17 Dexterity saving throw or take 18 (4d8) fire damage and be poisoned for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself with a success. The ouroban has advantage on attack rolls and ability checks against a creature poisoned by its Abyssal Fires.