Board Thread:General Discussion/@comment-25934096-20150306152535/@comment-184.174.131.177-20150309143644

The different stages of each Nightmare Rift Overseer's challenge are vastly different in difficulty. The first stage of a challenge (such as Broken Shell-1) is designed to allow players in the early stages of the game to survive. Enemies in the first stage range from 1000 to 6000, depending on the enemy (besides the Overseer).

As you increase in tier, the difficulty increases exponentially. Broken Shell-2 is for players that are most of the way through the campaign and have all 4 star units and higher. Broken Shell-3 is for players that have nothing but 5 and 6 star units, and the 5 stars would best be evolved to +2.