Behind Percy, something rustled in the wheat. Piper saw the tip of a black wing, and Percy began to turn toward the sound.
“Ignore it!” she yelped. “Look at me.”
Percy obeyed. “You cannot stop me. I will kill Jason Grace.”
Behind him, Blackjack emerged from the wheat field, moving with surprising stealth for such a large animal.
“You won’t kill him,” Piper ordered. But she wasn’t looking at Percy. She locked eyes with the pegasus, pouring all her power into her words and hoping Blackjack would understand. “You will knock him out.”
The charmspeak washed over Percy. He shifted his weight indecisively. “I…will knock him out?”
“Oh, sorry.” Piper smiled. “I wasn’t talking to you.”
Blackjack reared and brought his hoof down on Percy’s head.
Percy crumpled to the pavement next to Jason.

The Mark of Athena, Chapter XI