Wrex turns to watch in surprise as the hydra erupts out of the water and starts messing up his allies. He quickly moves to intercept the creature, knowing that while he cannot kill it, he can certainly buy his allies time and make them harder to hit. As he runs to join the fight, he begins to roar loudly, hoping to grab as much of the hydra's attention as possible.
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Double Move to get to the square adjacent to the hydra on its upper right side. I think I counted those move spaces right! If that's not it, Wrex will try and get as far down the path as he can.
Swift Action: Iron Guard's Glare stance. Hydra takes a -4 when it attacks anyone that isn't Wrex so long as it is threatened by him.