Sunlight Sensitivity. While in sunlight, the blight dragon has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Spores. Whenever the  blight dragon takes damage, it releases a cloud of spores. Creatures within 5 feet of the dragon when this happens must succeed on a DC 16 Constitution saving throw or 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 on a success.

Multiattack. The blight dragon makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 17 (2d10 + 6) piercing damage. If the target is a creature, it must succeed on a DC 15 Constitution saving throw against disease or become poisoned until the disease is cured. Every 24 hours that elapse, the target must repeat the saving throw, reducing its hit point maximum by 5 (1d10) on a failure. The disease is cured on a success. The target dies if the disease reduces its hit point maximum to 0. This reduction to the target's hit point maximum lasts until the disease is cured.

Claw. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) slashing damage.

Blight Breath (Recharge 5–6). The blight dragon exhales black blight in a 30-foot cone. Each creature in that area must make a DC17 Dexterity saving throw, taking 56 (15d6) poison damage on a failed save, or half as much damage on a successful one. A humanoid reduced to 0 hit points by this damage dies, and a lemure rises from its corpse and acts immediately after the dragon in the initiative count. The lemure is under the dragon’s control.