Where is hydra in aqw

The hydra is located at Lake Bonfire in Chiral Valley. Go to it directly by typing /join hydra in the chat box.

If you have already completed the hydra quests, you can use your Book of Lore to go back. Open up the book and select the "Story" tab. Select "Chiral Valley" and then pick "Battle the Hydra" in the second tab.