Boss's Movement is 3 and Range is 1, so using ranged character is a good choice
If you have a character with "Targeted" skill, the boss will only move to attact him and spare other character even if they's in range (But if he's adjacent to one of your character after moving, he'll attack)
Critical attacks will ignore the boss's 9000 def, so it's vital to use characters with high critical %
The boss's starting stats is high, but grow stats is very low, so the further you advanced, the easier this battle become
From the second time onward, each time your clear this map an additional Mad king will be added
From patch 1.04, after clearing this map 25th times the Mad king will become Crazy king with 900k Atk, Def and Res. All attack will be ineffective unless it's critical attack.