The Curse of Wasting is a particularly vile piece of dark magic created by a forgotten devil aeons ago. It may only afflict one entity at a time, and it progresses in phases. You progress to the next phase after meeting the conditions for that phase and completing a long rest. The effects are cumulative between phases

Removing the Curse. This curse cannot be removed by ordinary means, such as the Remove Curse spell. The only way to remove this curse is through the effects of the Wish spell, or by speaking the true name of the devil that created the curse while the Greater Restoration is cast on you.

Transmitting the Curse. When you remove the curse from yourself, you must speak the name of a new host who starts at Phase 1. If you are slain by a sentient creature while cursed, the curse will pass to that creature. If you die outside of combat as a result of this curse, it is passed to a random living person you know personally. 

Phase 1. You reach phase 1 of the curse automatically after receiving it. 

• Whenever you complete a long rest, make a DC 13 Constitution Saving throw. If you do not spend at least 8 hours sleeping during a long rest, you make this saving throw with disadvantage. After each long rest, if you failed the Constitution saving throw from this curse, the maximum number of hitpoints you can restore from the long rest is 80% of your hitpoint maximum. 
• Health restored by hit dice and and magical effects is reduced by your proficiency bonus.  
• If a spell or effect would cause you to gain temporary hitpoints, reduce that amount by your proficiency bonus.

Phase 2. You reach phase 2 of the curse after you learn information about the curse by magical means, such as through the Legend Lore spell, if you attempt to remove the curse using lesser spells like Remove Curse or Greater Restoration, or after you are reduced to 0 hitpoints for the first time after becoming cursed. 

• After each long rest, if you failed the Constitution saving throw from this curse, your Constitution score is reduced by 1, to a minimum of 8. 
• Your natural constitution score cannot be changed by magical means. If a magic item would set your constitution score to a fixed amount, it cannot increase it past 8 + your current Constitution score. 
  For example, an item that normally sets your Constitution score to 21 could not improve your Constitution past 18 if your base Constitution is 10.

Phase 3. You reach phase 3 after failing the constitution save to resist the curse three times consecutively while in phase 2 and while having a natural constitution score less than 12. 

• The DC to save against the curse is increased to 15, and you must sleep for 10 hours to complete a long rest and avoid rolling with disadvantage. 
• After each long rest, if you failed the Constitution saving throw from this curse, roll 1d6. Your Constitution score is reduced by half of the result, rounded up. There is no longer a minimum Constitution score from this effect, and your Constitution can no longer be increased or adjusted by magic items. 
• The impact of your Constitution Modifier on your maximum hitpoints is doubled.  
• Health restored by hit dice and magical effects, as well as temporary hitpoints you would gain, are reduced by half. Completing a long rest only restores half of your maximum hitpoints.

Destroying the Curse. In order to destroy the curse and end it permanently, you must carve the name of the devil that created the curse into your flesh, before coating it in the freely-given blood of greater devil and having the Greater Restoration cast on you while standing on ground that has been sanctified by a celestial. Once this ritual has been completed, the millennia of pain and agony experienced by those with the curse manifests as an Avatar of Suffering. Once the avatar is destroyed, the curse is lifted permanently.