Wiktionary
n. (context idiomatic English) a pessimistic person who often sees the possible calamity in every situation.
Usage examples of "prophet of doom".
A bearded prophet of doom clutched at her and ripped the network of small plastic disks that was her garment this morning.
In a savage voice he instructed Armadale, standing behind him, to capture the prophet of doom and give him a good thrashing.
The sound of the gang was diminishing into the distance, and the prophet of doom, restored to eloquence, was sending threatful bolts of damnation, hell-fire, and a brimstone gehenna hurtling after them.
And I had come across like a lunatic prophet of doom' I couldn't have done worse if I'd been carrying a sign proclaiming the end of the world.
We entered a strip of open woods, startling a crow who rose, cawing like a prophet of doom.