Inescapable Malady

You infect your target with an arcane disease. At any time after you cast this spell, as long as you are on the same plane of existence as the target, you can use an action to deal 7d10 necrotic damage to the target. If this damage would reduce the target to 0 hit points, you can choose to leave it with 1 hit point. As part of dealing the damage, you may expend a 7th-level spell slot to sustain the disease. Otherwise, the spell ends. The spell ends when you die. Casting remove curse, greater restoration, or heal on the target allows the target to make a Constitution saving throw against the disease. Otherwise the disease can only be cured by a wish spell.