And if you're building your deck to be technically in bounds by the card guidelines but substantially stronger than what other people are doing at that bracket so you can stomp them, then you are being a bad actor
Turning creatures face up is a special action you can take whenever you have priority, so you can attack with your creatures face down and turn them up after blockers are declared
The card mirrors this perfectly, stripping abilities from all creatures and shutting down death triggers and extra value engines
If it lives to your next upkeep it allows you to put any creature from a graveyard into play under your control as a Phyrexian
In a casual format like Commander where people like to play with big, splashy cards and fun creatures, an enchantment like Humility can completely turn the game on its head with a powerful effect that nerfs most commanders and popular creature cards into oblivion
Murderous Redcap: needs no introduction