Harpy

They come down onto the table rather than onto the people, and that is the point of them. Harpies snatch, foul and ruin - the meal, the stores, the water butt, the bandages - and they are gone up into the rocks before anyone has drawn. A party that fights one off and congratulates itself will discover the actual cost three days later, four days from anywhere, with nothing left to eat.

Snatch and Foul: slashing, melee 5 ft, +3 to hit, 2d6+2 (two strikes with claws), and on any hit it takes or spoils one item of food, water or supply rather than pressing the attack. Stench: 10 ft, save Con Tough, fail save roll 2d6+2 poison and the target is Weary until it rests, cooldown 3 rounds.

Takes and Goes: it disengages upward after any successful snatch and will not stay to fight a party that has nothing left worth taking. Ruin, Not Slaughter: everything it spoils is spoiled permanently - no roll, no save. Rations, waterskins, poultices and spell components are simply gone, and the DN should make the party account for them.