In ascension > 0, there are three keys you can collect through the run by choosing them in lieu of other rewards. If you get them all, there's an abbreviated Act IV to play: a hearth, then a shop, then a special elite, then the Heart. The Heart is much, much more difficult than the Act III bosses.

You don't need Ascension, just to have unlocked Ascension. With that said, I swear it's easier to beat the heart on A1 than A0 because of all the elite rewards.

The heart itself, well it's definitely challenging, but it only works for very specific builds. I went to some effort to beat it once on each character and basically have no intention of doing so again.

A1 is generally easier than A0 for exactly that reason.

If you want a meme deck, A1 is the sweet-spot.

Interesting. Is there an incentive to go that route beyond just saying you managed to do it? Not that I need more than that, just curious.

There’s an achievement (per character), as well as it being the « true end » of the game (and it increases the challenge as you need to beat a buffed elite, sacrifice a chest and sacrifice a hearth).

The heart was added in an update maybe 2 years ago. If you had the game longer than that, it wasn't unlocked automatically. Call that a bug or bad user experience.

Suggest you google how to unlock the heart and replay whatever needs to be done. It's really not intuitive if you already got all the characters and cards.

It's been a while since I've played, but if my memory is correct you have to collect 3 keys, each obtained by sacrificing an opportunity to improve the run (Pick it instead of a relic/rest/something else)

Technically the green key only calls for an extra challenge in facing a buffed elite instead of sacrificing, at least in the latest version.

Blue you get from a chest. Pretty easy in the Act 3 since it's likely the alternative relic is trash by that point. Green is the buffed elite. Again pretty easy in Act 3 because if you can't stomp it you're definitely not beating the heart anyway. Red is forgo a rest stop, which can be done anytime but I usually do it before the boss, especially if the boss is Hexaghost, because why both resting just to buff the boss?

> Technically the green key only calls for an extra challenge in facing a buffed elite instead of sacrificing, at least in the latest version.

I don't know if the latest version changed this, but the green key was definitely also a sacrifice -- if you look at the map, paths that allow you to get the green key have one less fire.