Gore crows causing Sabriel and Mogget to crash their Paperwing, in Sabriel.
Gore crows are a form of Dead Hand, involving any number of normal crows killed with ceremony by a Necromancer, then imbued with a single spirit from Death. While this could simply result in a single crow with a single spirit, more often the spirit is shattered among many crows. They then attack with the force of numbers. Gore crows can also be used to spy on the necromancer's enemies.
The more crows share a spirit, the more quickly the corpses erode, but they can last remarkably long without feathers or even wings -- they fly by Free Magic, not their own power.
Gore crows can be defeated by banishing the spirit fragment in one crow. The rest will follow into Death.