Hydra

Most people just run from Hydras, which is a great idea, but there is a way to kill them. The solution was discovered by Heracles, who once had to defeat the monster. You should first build a fire; it is crucial that a fire is present before proceeding. You then cut off the heads, I'd start with the middle one, and burn the stumps THAT ARE STILL CONNECTED TO THE BODY (people have made the mistake of burning the severed head).

-Annabeth Chase, Daughter of Athena