Choose a necromancy spell of 5th level or lower that you can cast, that has a casting time of 1 action, and has a range of Touch. You cast that spell—called the contingent spell—as part of casting contingency boils, expending spell slots for both, but the contingent spell doesn’t come into effect. The contingent spell is stored in a boil on your skin that is created as part of the casting of contingency boils. Each time you cast contingency boils, you create a new boil on your skin.   Your skin can contain a number of contingent spells within boils equal to your spellcasting ability modifier. For each boil on your skin, your Charisma score is reduced by 2 until you no longer have any boils from this spell on your skin. When a creature within 5 feet of you deals damage to you with a weapon attack, you can use your reaction to rupture a boil. The contingent spell takes effect immediately after the rupture, targeting the attacker. That boil and that instance of the contingency boils spell then ends.   If you are affected by Lesser Restoration, Greater Restoration, or a similar effect that removes diseases (such as a paladin’s Lay on Hands), all your boils are immediately cured and all instances of the spell end, removing all remaining boils and their stored spells.