Who sent echidna and the chimera to attack Percy?

In the *Percy Jackson and the Olympians* series, Echidna and the Chimera were not sent to attack Percy. They were part of the forces of Kronos, who was trying to overthrow his father, Zeus, and take over the world.

Here's the breakdown:

* Echidna: She was a monstrous being who birthed various other monsters, including Typhon, Cerberus, and the Chimera. She was a servant of Kronos.

* Chimera: A fierce creature with the head of a lion, the body of a goat, and the tail of a serpent. It was one of Echidna's offspring and part of Kronos' army.

Percy encountered Echidna and the Chimera in *The Sea of Monsters*, where they were part of Kronos' plan to destroy Camp Half-Blood. The monsters were not specifically sent after Percy, but they attacked him because he was a powerful demigod standing in the way of Kronos' goals.