I would prefer to get Sir Jing's weapons or the Legendary Magma weapons to kill the
Hydra's.  To get Sir Jing's weapon, go left of the Oaklore keep. There will be two knights
and a catapult.  There will be a quest called Sir Jing's weapons that will get you the Sir
Jing's weapons.  To get the Legendary Magma weapons, you need 500 gold and go to the
weapons shop.  To get to the Hydra's, you need to kill 3 Renegade Hunters, and a
bear(there pretty easy).  When you get to the middle of the brigde, you will have to fight
the Hydra's to pass the bridge.  The Hydra's on the side do more damage than the middle
one.  I suggest you kill the side ones first.  Then, kill the middle one.