Strix

Strixes are mythical creatures that feed on human flesh and blood and will curse whoever kills them. If their talons scratch someone, the person will be paralyzed, as demonstrated in the First chapter of The Burning Maze. According to Apollo, or Lester Papadopoulos, They will "dis-disembowel you, drink your blood, and eat your flesh" if you let it attack you.

The Burning Maze
While in the Labyrinth with Grover and Meg, they stumble onto a group of strixes. In an attempt to flee, Meg and Grover create a plant barrier to seal the creatures in the tunnel. Unfortunately, one Strix flies through the gap and attacks Apollo, scratching him on the cheek, which paralyzes him.