Custom mode now has one of the long-demanded options: endless mode. I think you’ll find that any deck capable of beating three bosses is capable of going quite a bit further, especially when you can pick modifiers to fuel that even further. You really should turn on blights, however, or else it really does become “endless” mode.
Blights are harsh negatives that replace boss relics. Without them, you can keep increasing your strength faster than the game itself ramps up. That gets boring. Blights make things a little spicier.
In endless mode, the importance of everything shifts: only scaling matters. Anything that is good but works by addition rather than multiplication is crap. The Defect’s Buffer card is normally pretty weak: prevent one attack. In endless mode, when enemies might do hundreds of points of damage, you might Echo-Amplify-Buffer+ to stop six attacks, which will give you enough time to win. But if you’re playing like I do, you go for the turn one win every time so damage doesn’t matter; Mind Blast or Perfected Strike with absurd numbers of cards is fun. And then you eventually hit numbers that are too big or just a really bad roll of the dice.
It can have that Civilization feel: one… more… floor…