Decaying Touch

You wreath your hand in necrotic decay, causing anything you touch to wither and die. Make a melee spell attack against a creature or object within range. On a hit, the target takes 1d6 necrotic damage and starts to flake and decay. The first time it takes damage from another source before the start of your next turn, it takes an additional 1d6 necrotic damage. Targets immune to diseases are immune to this effect.

The initial and secondary damage of the spell increases by 1d6 when you reach 5th level (2d6), 11th level (3d6), and 17th level (4d6).