Chimera

The Chimera is the son of Echidna, the mother of all monsters and the wife of the evil Typhon. It has the head of a lion, the body of a goat, and a snake-headed tail.

History
In myth he was killed by Bellerphon on Pegasus when Bellerphon jammed a lead ball into its mouth. The ball then melted, suffocating it.

The Lightning Thief
In The Lightning Thief, Percy Jackson is cornered by a fat lady and her chihuahua at the top of the St. Louis Gateway Arch. The lady constantly refers to her pet as "sonny" or "son" and it is only when Percy is forced to wait for a second elevator down and left without the company of Grover Underwood and Annabeth Chase that he discovers who the fat lady really is.

The chihuahua transforms into his true form, that of the Chimera, and attacks Percy. As Percy tries to defend himself and a few innocent bystanders with Riptide, he is outwitted by the creature and ultimately forced to dive out of the Gateway Arch (via a hole conveniently provided by the Chimera) into the muddy Mississippi after being poisoned by the snake-headed tail.

Powers
The chimera has many powers including:


 * It can breathe fire.
 * Its snake-headed tail has venomous fangs.
 * Fast like a lion
 * Hard to kill

Trivia

 * In The Lightning Thief, the part where Percy and his friends encounter Chimera and Echidna was replaced with them fighting the Hydra at a replica of the Parthenon in Tennessee.