Lvl 31 on endless with Juliet-A (ela +25), 3 Shadow killers (attack +30 +15 +15) and a Devourer (hp 500+350+350). Got the badge after around 10 tries. First try - lvl 24, then it was mostly 15-20-ish. I guess it depends on how lucky you are with the power of waves.
Anyone else stuck in the level with 8 lying sideways on their way back? I entered the level and there were no shadows of previous me. Had to reset the game but I don't think I'm going to do it again anytime soon since I nearly crushed my keyboard in rage while trying to beat this game for the first time -_-'
Wow, this is surprisingly funny. You know that it's not easy to make a good idle/clicker game after cookie clicker or dr.meth. I like the idea with levels and time limit to defeat bosses. Good job!
 "STUG")
 "Idle Grindia: Dungeon Quest"){kind=icon}
 "Badge Emperor")
 "Pocket Creature PVP")
 "Slayaway Camp")
 "Mytheria")
 "The Adventures of Red")
 "One Step Back")
 "Crush the Castle Players Pack")
 "Death Dice Overdose")
 "Decision 3")
 "Clicker Heroes")
 "oO")
 "Soccer Physics")
 "Snail")
 "Music Catch 2")
 "Coinbox Hero"){kind=icon}
 "The Peacekeeper")
 "Open Doors 2")
 "Brawlin' Sailor")
Got to admit though that it makes the final kill just so good and satisfying. :)