The Dire Corby is one of those monsters that does not look like much on paper. Then you use it at the table... and it changes everything.
It comes from the Fiend Folio. It is a tall, black-feathered humanoid bird with claws and muscle. It does not speak. It does not cast spells. It just charges in and screams one word over and over again... “Doom”.
That is its language. That is its personality. That is its tactic.
Dire Corbies fight without fear. They do not break. They do not hesitate. They come in flocks. They leap into the middle of your party and claw until someone drops. Then they move to the next.
They live deep underground. That makes them perfect for caves, ruins, and forgotten temples. You can use them as native threats. You can use them as shock troops for something smarter. Or you can let them be the top predator in a sealed cavern system... until your players break that seal.
If you want to turn it up, use sound. That chant. That word. Doom. Let it echo ahead of the fight. Let the players hear it... over and over... getting closer. Let them wonder if it means something more.
The Fiend Folio is full of strange monsters. This one is simple. And it works. It does not need magic or tricks. It needs darkness, claws, and the confidence to run full speed into a wall of steel.
Use it once. Make it loud. Let the players remember the word.