Slay The Spire

don't pick up any cards for battles UNLESS it's True grit Havoc or Purity.
At shops remove a card whenever able and only buy if it's one of the above.
Should only be 1 designated run.
https://slay-the-spire.fandom.com/wiki/True_Grit

Got this with Second Wind and Purity. If you're struggling and have a rest site soon, Purity+ exhausts 5 cards instead of 3.

Couldn't get it. I had 0 card but did not pop

I got lucky with two True Grits early on and the next enemy was a slime so I just left one of the mini slimes alive and used those to dwindle my deck down to three.

I'm pretty sure I got this with 4 cards. It appears to have unlocked as I was playing a card. I had 4 in my hand, I played one, and there must have been a split second between when I was discarding it and it only recognized 3 cards in my hand and none in my draw pile or discard pile.

I got a true grit early on, found some low level baddies, killed all but one, which only did 7 or less damage, and then just slowly used true grit until it popped. Easy.

I just had kind of the same experience as @Xtowers. I definitely had way more cards than 3 combined across the various piles and it popped as my deck was being shuffled back from the discard to the draw pile.

Met the criteria but it wouldn't pop even after quitting out and trying multiple times. As soon as I finished that battle and did it again in the next encounter, it popped under the same condition that @Xtowers mentioned. So if it isn't working for you, finish a fight and try again on the next one.

You actually don’t even need any specific card for this. I did it with just a swift potion and elixir. Look for them in an early shop and take the obtain 3 random potion blessing if offered.