Hemosumeric Rites

Ancient rites long abandoned by most mages; the caster sacrifices their physical health to cast magic of a higher order. These arcane rites can be learned and utilized by any spellcaster with the Ritual Casting feature, and the spells which can be improved via these rites must be from the same class's spell list as the Ritual Casting feature. 

When casting a spell of 1st-level or higher with a casting time of one Action, the caster can additionally spend their bonus action to activate the Hemosumeric Rite, increasing the value of the spell slot expended in the spell's casting by one or more. At the end of the caster's turn after the spell has been cast, the caster sufferers 2d8 Necrotic damage, which can not be reduced in any way, plus an additional 1d8 Necrotic damage for each additional level increase to the spell slot. The caster's hit point maximum is reduced by an amount equal to the amount of damage taken to a minimum of 1 until the end of the caster's next long rest, this effect can be ended early by the wish spell or the greater restoration spell. Additionally, the caster suffers a level of exhaustion for each level of increase to the spell slot. A caster can do this a number of times per day equal to their proficiency bonus. 

When increasing a spell slot in this way, if the caster's level of exhaustion is increased enough to kill the caster, the caster instead falls unconscious and must complete a long rest to recover from this effect. The caster still suffers the damage and hit point reduction effects. Additionally, this feature may not be used to increase the spell slot value of a spell that you do not already know, such as a spell from a spell scroll.