You will apparently be able to claim a whole range of valuable rewards and free content - some of which are valued at $400 (in-game value) - by logging into your Prime account through the special in-game menu tab.
In addition to this, players can now take on a new world boss challenge against the so-called Enraged Giath, the Goblin Chief. This guy is apparently the Supreme Chief of Goblins and resides in a deeply-secluded corner of The Forest of Plunder. Upon defeating this monster, you’ll get your hands on a Giath’s helmet fragment.
To find out more information about this neat promotion, have a gander at the official website.
Source: Black Desert Mobile
