2056ab3d_Guide___Kings_and_Legends_Wiki__Description
[Upgrade to] Level 40 [Unlocks] Desert Fortress, Castle of Bones [Rewards] 90 1 [Description] 
Desert Fortress & Castle of Bones can drop unique equipment, up to Legendary rank cards, Gold and Silver. These Boss Fights are very difficult, take allies!
Game Guide - Kings and Legends Wiki
Description