If you're having trouble getting the hard badge, enable hardcore mode on endless mode. This will allow you to rack up points much faster than normal endless mode.
Party Sequence: Soulseeker, ShadowDragon, ShadowDragon, EntropyAlien, Devourer
This build once brought me to stage 47. Devourer up front +500 HP, 350 HP, 200 HP gems. Two ShadowDragon, one with 30 Atk, 15 Atk gems and the other with 15 Atk, 15 Atk gems. Soul Seeker with 40 Ela, 15 Atk & 10 Atk gems. EntropyAlien with 15 spd gem. (higher gets em killed too quick).
TO FIND MASTERs: Master where art thou? Masters are located in Old quarter (intro and fairgrounds), Greyed quarter (tower) Working quarter(mine) and Central quarter(outskirts) You can visit these locations in any order you want, the order of the masters will still be the same : if you missed the one in Greyed Quarter, and found the one of Central quarter, your master of pain will be at the Greyed Quarter.
IF YOU'RE STUCK in the first 3 sections and have completed it 100%, you need to complete one attack from the tower and the new areas will be unlocked.
Took me a while to figure this out, hope this helps. Please + this so everyone can see this.
Master where art thou?
Old quarter (intro and fairgrounds),
Greyed quarter (tower)
Working quarter(mine)
Central quarter(outskirts)
You can visit these locations in any order you want, the order of the masters will still be the same : if you missed the one in Greyed Quarter, and found the one of Central quarter, your master of pain will be at the Greyed Quarter.