This is the easiest build for me, Ogres tend to path bug and most of them stay down the valley and the Boss is perfectly place. You do need a lot of range for this to work.
Wave 1 : I first build the auras , the buff beam, the reflecting beams, the 3 LT's
Wave 2: I stay on my Apprentice, get mana then build the 2 fire, after that the DST's.
Wave 3: Complete the build then get on a Monk Tower Boost with a Genie Pet to upgrade
2 - During boss fight this wall must stop the Boss damage and protect the Apprentice towers. If this walls breaks its game over.
3 - I stay there with my Monk Tower boost during the fight. You can repair the wall at 2 if needed.
4- I park my builder Apprentice there.
5 - The Crystals
Once you have a Genie Scimitar you can go farm Divine Crystals in Assault Challenge Pack: Part 2.