Run for your Life! Secret Achievement
Right After Act 1 is finished you can get this.....
First off, head over to Sapi-Res Nome and scan the river with your Eagle to find a group of Hippos. When you find them, tag, and set your custom marker. Head over via Fast Travel or Mount. Simply run up to them and make them charge you and run away!!! When your out of conflict, run right back and repeat....