This achievement requires that you end a run with zero cards in your deck. No spells, creatures, champions - all must be PURGED (not simply consumed). I have no idea how someone would ever manage to do this in a normal run of the game - but thankfully we don't have to. We'll be using a seeded run that was posted by rjr619 on Steam instead:
From the main menu, select:
- Community Challenges - Play
- In the Join Challenge section type in: IrishOccurPraise
- Hit the right arrow button
Pick Up Thorn Fruit initially and play Stings throughout the run. There is an artifact shop (Merchant of Trinkets) about half way through has both the sting relics in it to pump up their damage. You will be forced to purge one card after each fight, but along the way hit a few Unstable Vortex to remove additional cards and pay to have some removed if necessary. Make sure you go into the final battle with absolutely no cards in your deck and your pumped up free Stings will be enough to win!