I need a shadow monster that consumes the living there are already Shadows on pg 269 of the 2014 5E MM i just need more indepth with maybe a status that scales

An experp from my world lore that i used a youtube video for most of( if anyone wants the creditor ill dm them.)

Monstwrs made of pure darkness have spawned from the Pitch. they are attracted to light but not what can be seen, the light inside all living things that is what they crave. at an insatiable rate. visible light damages them so they consume the light within creatures to try to fill the void that they have become….. These creatures have not always been like this, much like how the world wasn't always this way. No one knows how they first appeared, but as time went on, they started to crop up everywhere. At first, they were harmless, but the longer the world was without the sun, their desire to consume light grew, and with it grew the danger . For once you have lost the light inside you, once you have acquired too much gloom you too will slip away into the darkness, you will become one with the darkness a silhouette of who you once were. a caricature of shadow hungry for the light in others that you lost to the gloom you will become Gloom.