The necromancer snaps zis fingers, a dead creature within range explodes with necrotic energy.   Each creature in a 15" radius sphere centered on the dead creature must make a Dexterity saving throw.   On a failed save each creature takes 2d8 necrotic damage + loses 2 from zis strength, or half as much damage on a successful one with no strength loss.   If a creature is reduced to 0 hit points with this spell, the creature explodes, repeating the same effect as this spell. If an undead creature is affected by this spell or its explosion, then it must succeed Constitution saving throw or explode, repeating the same effect as this spell a number of times equal to half its CR (a minimum of 1 time).