Making A Broodguard

Yuan-Ti make broodguards from captured humanoids. Each subject is fed a special potion that immediately renders it incapacitated and transforms it into a broodguard over the next 1d6+6 days. A subject forced to imbibe the brew can make a DC 15 Constitution saving throw, on a success, it takes 14 4d6 poison damage and isn't otherwise affected.
A spell such as Lesser Restoration or Remove Curse can end the transformation process at any time before it runs it's course. After the process is complete, only a Wish spell can reverse the effect.