DreamWorks Dragons: Legends of The Nine Realms

Challenge Difficulty is unlocked on a level after you have done both the blue and orange routes in a level. You can level up your dragons to be far stronger before attempting to make them easier. This achievement is for completing challenge on all five levels in the fifth world called Dark Realm. These levels provide little difficulty. Level two was the hardest. Skip all enemies unless in a zone, and exploit enemy’s weaknesses. I had all dragons maxed out and did them all first try.