Incorporeal. The ghast is completely incorporeal. It is immune to damage and cannot be affected by spells or other magical affects. While it is incorporeal, it cannot use its standard damage dealing attack; it can only use its corruption ability. 

The ghast can be made corporeal only by using the Blessed Sickle magic item.

Bound. The ghast is bound to the place it originally died, and it will not move more than 120 ft. away from that spot.

Cursed. Anyone killed by the ghast is immediately raised from the dead as a ghast. Nothing can release a soul from being a ghast short of True Resurrection or the Wish spell.

Eternal. If destroyed, a ghast will repsawn in the place it was originally killed within 1d4 days.

Corruption. Ghasts can smell any sort of edible food from miles away. The ghast can use its action to reach its incorporeal hand into a rations bag and corrupt one day's worth of rations, turning it into a useless pile of green slime. If someone is not carrying any rations, the ghast will suck the life out of a creature directly, which will cause the creature to become supernaturally hungry. The creature must eat one day's worth of rations within the next hour, or it will gain one level of exhaustion. This effect can stack; a creature who is hit by the corruption ability three times during an encounter with ghasts will need to eat three day's worth of rations within the next hour or take three levels of exhaustion. This attack can only be used while the Ghast is incorporeal. 

Death Claw. Melee weapon attack, one target, 5 ft. range. +5 to hit, deals 7 (1d6 + 3) necrotic damage on a hit. Can only be used while the ghast is corporeal.