Yeah, 999 is the cap. I took 0 damage from the heart. The build is based around the following cards:
- Barricade: Block value (what you call armor) is kept from turn to turn (normally it’s reset to 0 each end of turn)
- Entrench: Doubles current block value
- Impervious: +30 block (+40 when upgraded)
- Body Slam: Deal damage with your current block value
I got lucky and drew Barricade very early, so I could really focus on block without having to invest in other cards to deal damage early on. Then I later received a Bottled Tornado relic, which lets you choose a power card that is then always in your hand at the start of combat. This was perfect for Barricade.
Then all you need is one of the Impervious cards and each Entrench you play after that just doubles your power. After a few hands your block is so high that you can kill every monster in the game with one Body Slam (except the heart, it has a damage threshold per turn).
The reason why I could get all those cooperating cards is because I received a prayer wheel relic early on. This gives you an additional card draw from normal monsters, so I could choose from 6 cards every fight instead of only 3.
On top of all this luck I also drew a Feed pretty early on. If you kill a monster with Feed, your max hp pool is increased by 3 (4 when upgraded). The high HP pool really helped me in some fights when the deck was unfavourably shuffled. To further exploit Feed, I also bought an Exhume from vendor. With this card I could play Feed twice every fight with more than 1 monster. Usually, you are happy if you can use Feed at all, because it has to be the killing blow, and if it’s not in your hand when the monster HP is low, you have to decide if the 3 max HP are worth more monster turns that will probably damage you, but with this infinite block build I could comfortably wait until it showed up in the right moment.
Now the question is this: Is it really good game design if it needs a huge amount of luck to beat the game? And that, if you do get lucky, the fight is so trivial that you take zero damage? I don’t expect to win against the heart ever again. I can usually reach it about every 3-4 runs, but beating it is very hard, because there is another fight right before it that normally leaves you beat up pretty hard and with no chance to recover.