The Goal to All Life is Death

You start concentrating for 18 senconds and an ethereal clock appears floating behind you, counting down while you concentrate. During this time, you can not attack or cast spells. When this time ends, the clock strikes 12 and explodes in a 240-foot-sphere, centered on you. All creatures, other than you, must make a Constitution saving throw. Each creature that failed the save or is a CR of 4 or less dies. Each creature that succeeds the save takes necrotic damage equal to half of their maximum health.

This spell does not affect constructs or undead.