Ooh, I've been trying to do this with same champion and challenges for a small while. Trying to get both the "3 or more challenges" and "beat final boss with badder bosses and all demon spawners enabled" badges. Failed each time, including twice getting to 25th floor but failing to beat Yog-Dzewa. Maybe I should be less ambitious and only try to get one badge at once...
After being able to consistently win without challenges, I activated three and then two challenges, only to consistently lose! I had to take it slow and learn new strategies for each challenge, and then learn to apply them all at once. You also need to be lucky and get the right equipment!
TLDR, take it slow and keep trying to improve your strategy, eventually you'll get there.
Thanks! I've won without challenge with each hero at least once, and once with a single challenge, but not with two challenges, maybe I'll try that first.
I am currently trying 6 challenges. It's hell. Actual hell. Went for what I think are the 6 easier challenges: Barren Land, On Diet, Into Darkness, Hostile Champions, Badder Bosses and Swarm Intelligence.
With mage, wanting to go warlock for the saturation benefits he gets, but the furthest I've reached has been leaving Tengu at 15-ish HP. I just needed 1 more healing potion... Dodged every single of his attacks, too. Ig it's just really hard to beat Tengu with 2 healing pots (had to drink the other few I had to not die, starvation REALLY hurts) and on a +1 leather.
Had other good run with better armor, was "ready" to enter Tengu, as I'd already explored every single bit of F9 (actually, I hadn't, Into Darkness leaves tons of dark spots) but died out of starvation.