Dealing with the centaurs - (Thanks to Mona Sax for clearing up a bit the procedure) You have to kill the two centaurs, but you cannot do it straight away. As you can see, they carry a shield that proctects them from your bullets. So, the first thing you need to do is to remove the shield from their hands. At the top right of your screen, you can see two bars. The yellow one is their health, which means that they die when the bar drops to zero. It will not decrease, however, before you remove their shields. The red bar indicates their rage. When you shoot repeatedly, the bar starts filling, causing the centaurs to become enraged. In that case, two things happen by turns:
• The centaurs stare at you, indicated by a green glow. You have to turn around and look the other way (or simply crouch - thanks Notts Raider). If you stay and look at them, the green glow will turn you into stone. Either the centaurs will kick you (and kill you) or you will have to press the arrow buttons and remove the stone from your body (and continue the battle).
• The centaurs attack and you have to use the Adrenaline Dodge and shoot their head. Remember: You have to press and hold the Crouch button, and when you see the red target on a centaur's head, shoot it. If you succeed, the centaur will slump down and expose his shield, which means that he will turn the shield and the ring at the back will face your direction. You then have to use the Grapple, catch the ring and pull the shield out of his hands. Once the shield is on the ground, the centaur will not pick it up again. Repeat the same procedure until the second centaur loses his shield.
Once both shields are down, start shooting the centaurs. This time, they will not attack. They will only use their green glow and try to petrify you. Once they become enraged and are ready to use the green glow, quickly holster your weapons, pick up a shield and point it to a centaur's direction. The green glow will reflect and return back to the centaur, thus turning him into stone. Quickly drop the shield and start shooting. You will see that the health bar will start decreasing. When it drops to zero, the centaur shatters. Repeat the same process for the second centaur.
Warning: To use the Grapple and catch the shield, the centaur must have rotated it and the ring at the back must face your direction. Sometimes, the centaur freezes and only raises his hand. In this case, you are not able to grab the ring and you have to repeat the process again. This screenshot shows the correct and "wrong" positions of the centaur's hand.)