The Hydra is a VERY large reaver that is rode by Skorge. It is seen several times through out the game but is fought only 1 time of the several experiences. The color of the Hydra is unique compared to the normal, average sized reavers.
After beating Skorge in a chain saw duel 3 times, his Hydra will pop through the large decorated window and Skorge will fly away on it. After you try to leave the Locust Hive, you use a Reaver with Cole if you are Marcus, or with Baird if you are Dom. While being chased in the tunnel, every now and then, you will hear one of your comrades telling you where to shoot. The main areas are his mouth or at the turret on top of it. Also, you can use your left analog stick in order to dodge the bullets or the missiles it shoots at you. You will know you have escaped successfully when the game goes into a clip and the Hydra gets stuck in between two large boulders. After you make it back to the surface, you should be on the last Act of Chapter 4 or the first Act of Chapter 5. While flying your reaver outside, you have to kill a bunch of Reavers, and then finally finish off the Hydra. When you kill the Hydra, you kill Skorge.
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