In the adventure Descent into Avernus, a module I run (with HEAVY modification), there exist a monster inside the soul intake of a wrecked flying fortress described as '30 foot long centipede' which uses the stat of a Remorhaz except necrotic.

There are no visuals for it, which is annoying for me, so I decided that even if it'll take a while before my players would come across it, I'd draw up a visual token for it maybe.

I decided to make it more wormlike than a giant centipede, and give it a weird flowering petal mouth with a skull-like maw inside of it, and it has its own vents that spews up soul dregs, which is the representation of its necrotic damage.