RAGE 2

Bonetower: Furorem is located on the left part of the map, the most southern one out of the three on the left. Clear the area, then a jumping spring will turn on and allow you to reach the portal. Once inside Furorem, you need to slay several waves of Skeletons to make the guardians appear. You will have to defeat 4 guardians to finish the Bonetower and obtain one of the missing shards.

Be careful in this tower the last guardian acts more like a separate boss that is unlocked after defeating the third guardian. It doesn't change anything but the area is more open and it's a lot bigger. However it can still be defeated very easily using the same method. 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 whilst you slash away and the overdrive will last longer.