Multiattack

The gray thirster makes two claw attacks and one Withering Turban attack

Claw

Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 6 (1d6 + 3) slashing damage.

Withering Turban

Melee Weapon Attack: +5 to hit, reach 10 ft., one creature. Hit: 5 (1d4 + 3) necrotic damage. If the target failed a saving throw against the Thirst trait at any point in this encounter, its hit point maximum is reduced by an amount equal to the damage it took from this attack. This reduction lasts until the target has no exhaustion levels.

Drought (1/Day)

The gray thirster draws the moisture from a 20-foot radius area centered on itself. Nonmagical water and other liquids in this area turn to dust. Each creature that is neither undead nor a construct in the area takes 9 (2d8) necrotic damage, or half damage with a successful DC 13 Constitution saving throw. Plants, oozes, and creatures with the Amphibious, Water Breathing, or Water Form traits have disadvantage on this saving throw. Liquids carried by a creature that makes a successful saving throw are not destroyed.