After the last pair of eyes is shown, Riven will move once more and return with the Taken material in her mouth. Shoot as much of it as possible, and she will take heavy damage. After she closes her mouth, Riven's outer shell will open again. All 10 eyes will be shown, but the six that were shown before have to be shot. If the wrong eye is shot then the team will wipe, and the encounter will start over (which is why it's best that one Guardian is only responsible for one eye). After all of her e...