Dzaram's Specter

When you cast this spell, choose a point in range. Crackling gray energy that resembles spiderwebs fills a 20' radius sphere centered on that point, draining life energy from each living creature in the area. Any creature other than a construct or undead that enters or starts its turn in the area must make a Constitution saving throw. If it fails, it loses 1 hit point per Hit Die that it possesses, and its maximum hit points fall by an equal number until the target completes a short or long rest.