Vampirism

By some means, you were afflicted with a vampiric curse on your very soul. As a result, you do not subsist in the same way that other creatures do. You cannot heal via rest, potions, or healing magic; and healing spells cast on you fail as if they had been countered by Counterspell. Spells that consume over 50 GP in material components are exempt from this rule. All your Hit Dice, regardless of what class they come from, are treated as D6s in HP calculation. You have resistance to necrotic damage, but vulnerability to radiant damage. However, when you deal necrotic damage, an affected creature must make a CON saving throw (DC is 8 + your proficiency bonus + an ability score of your choice.) On a failure, its Hit Point maximum is reduced by the amount of damage it took, and you regain that same amount of Hit Points (round down). A creature regains its former Maximum Hit Points after taking a Short or Long Rest or after having the Remove Curse spell cast on them. On a success, nothing happens. If you have Advantage on such an attack roll, the target has Disadvantage on their saving throw unless they are a construct or undead. If the target rolls a 1 on their saving throw, you heal for the full amount of necrotic damage you dealt.