RAGE 2

The Tristitia Bonetower is located to the furthest right of the Cabin. Clear the area, then a jumping spring will turn on and allow you to reach the portal. Once Inside Tristitia you will need to slay waves of Skeletons in order to make the guardians appear. You will have to defeat 4 guardians to finish the Bonetower and obtain one of the missing shards.

The easiest way to kill any guardian is to go into overdrive with the sword. Keep up a high multiplier by attacking them and the horde of skeletons around you at the same time. Use Shatter and Slam for extra damage. This way your life with constantly replenish while you slash away and the overdrive will last longer.