Slay The Spire

If you're at the point where you're trying to beat the heart (no pun intended) in Act 4, you know by now that there are many possible random card and Relic combinations that may pop up during your journey. Therefore, a single and direct solution to this achievement probably isn't possible. What is possible is getting some advice on the best way to earn the victory, so here you go.

Act 4 Access
Getting to Act 4 first requires you to complete Act 3 in Standard mode with all 3 of the playable characters (Ironclad, Silent and Defect). This is a mandatory pre-req for this achievement. Once that is done, you'll see a triangular icon next to your name in the top left of the screen during all your runs. There are 3 components to it, which represent 3 keys: Sapphire, Ruby and Emerald. To get to Act 4, you need to obtain all 3 keys before completion of Act 3. Each key is obtained in a unique, yet consistent style.

Sapphire
This key is found in all non-Elite chests and will always be linked to a Relic. You can pick either the key or the Relic. This combination will be available through the end of Act 3, so don't necessarily take the key as soon as you can. Wait for a time until it's linked to a Relic that doesn't interest you.

Ruby
All Rest sites will have the option to Recall. Selecting Recall will get you the key. Like the Sapphire tip, get this key when it makes sense to do so.

Emerald
A slightly updated Elite icon on your map identifies this key's location. It's represented with an animated flame. This Elite will always drop the Emerald key as a prize upon your win. Unlike waiting for a later time to get the previous 2 keys, I find it's usually best to get this key out of the way in Act 1.

Ascension Levels
Going with Ascension Level 1 is a good option to get more Elites mixed in: more Elites = more Relics. Don't necessarily attempt to hit as many Elites as possible when you pick your path. Use good judgement based on your health and your path choices.

Card Advice
I find the best way to proceed with Ironclad is to primarily focus on your defense. One core card you should have is Barricade. It allows you to save your block between turns. Good counterparts to Barricade are Entrench (double your block), Metallicize (gain block at the end of each turn) and Impervious (massive block gain). Snag a Feed (damage and max HP increase) if you can. It’s a great option for growing your max HP.

You're going to need some offense too of course but keep it smart and minimal as you make your way up the floors. Remove standard cards from your deck as you go. Body Slam (deal damage equal to your block) is an obvious and definitive card to get in your deck. I also go for Headbutt (damage and add a discarded card to your draw pile), Dual Wield (copy and add an attack or power card) and Flex (gain strength). Choose your Attack cards wisely. Don't go and take anything and everything that's offered. Always skip taking cards unless they'll be a good fit for your deck.

Another good tip is to obtain Armaments as soon as you can and upgrade it. Its upgrade allows you to upgrade all cards in your hand. With a smaller sized hand, it's quick to have many cards in your deck upgraded during each combat. This method allows you to skip card upgrades, which will save you gold and allow you to go with the other options that are available when you're presented with a choice for an upgrade. Also, if Apotheosis ever appears, snag it. This card upgrades ALL CARDS in your deck. I scored a chance to make that Innate (start every combat with it) and it was the first card I played during every combat.

For the final battle with the heart, quickly get your block up as high as possible and drop some Body Slams.

Here's my run: