Not sure if luck or amazing at game (it's both).
FIRST: Just because I completed this and I have a good strategy doesn't mean it's not a terrible challenge. Guarantee that MA and BURNDAYRAZ spawns on the middle Island and this would be a really neat challenge level.
As it stands you need to find a good leveling glyph right next to you at spawn (HALPMEH for me) and then you need to stumble on to MA without wasting too many dark tiles. Also you need MA to actually spawn, which she has a chance of not doing.
@Avatar: Here's the trick. Get to level 8. At level 8 your fireballs do 32 damage, so you can regen 3 dark tiles without The Undefeatable's health getting away from you (because he's on 1 health, 3 tiles = 30 health which leaves him at 31, just low enough to kill him with a fireball).
Here's the rythm. While you can't attack him because he'll 1-shot you go: (assume he starts at 1 health, you'll need to use pots/refreshment to get him there) regen 3 tiles, fireball, attack something else, regen 3 tiles, fireball, attack something else.
Use mystic balance for 5mp fireball. With this strategy each cycle only costs 2 mana. It's pretty easy to hit 18 mana if you get MA. 9 cycles of this removes 18 death protections. A couple of mana pots (with more cycles) and you can get him down to within attacking range.
Then do it again.
I had a health potion left over, the only thing I bought from shops was the Gloves of Midas, I didn't use the apothecary. Also, I used 2 refreshments before fighting The Undefeatable to kill a couple of good level up targets (if you look in the screenshot before, one on the level 9 snake and 1 on the level 7 Djinn).
Dark space was way more important than popcorn. I think that's why this level seems ridiculous and rubs us the wrong way. Just get to level 8 asap without using too much dark space.
I started fighting the boss when I killed the level 3 imp a level 8, I finished his first form off after the first level 1 AA at level 8.
edit: Oh, and the reason I think binlor is here is with knockback + burning you can shave off 3 death protections with 1 attack. You still need to burst him down to damage dealing range though.
edit2: Just realised, if you take Flames from MA you can start doing this at level 7.

