Hertz Locker is a Feat of Strength achievement that can be earned by completing Mechagon with all hard modes and without anyone dying.
We only tried three different nights and ended up earning it last night – the last night before it became unobtainable when the Shadowlands pre-patch hit. We had a few hiccups because for some reason, despite being able to do 15s no problem, we still learned of new mechanics that would cause a death – on trash! I’m looking at you shrink ability that can cause someone to get trampled by their friends.
I’m glad we got it in the nick of time!