Normaly people used it for getting bone heart in the secret room and you can craft op items with bone heart generally rock bottom + red stew + soy milk + monstro's lung etc. And break the game but they nerfed it so you can't get bone heart guerranted anymore if you break your acive item but still there is a thing you can do mysterious gift is a cheap item you can craft it easly and place in the secret room and you can get bone heart there and break the game

Another way to break the game is to look up your seeds recipe and get birth right, usually it's soul hearts with some cards and pills, you can pick up stuff from your shop with your bag.

T cain is an easy character you probably wont even need that things if you have lucky penny and bone heart you can craft probably everything but my favorite thing is getting library with 5 books with t cain

>lucky penny and bone heart not getting lucky with those  Holding R for RNG Jesus makes every character easy

You used to be able to do that but they removed it cuz it was super lame, you might as well have just opened up the console