Slay the Spire 2 patch fixes RNG bug a player spent 8 hours proving exists

Mega Crit dropped a major Slay the Spire 2 patch that fixes a significant RNG bug, introduces a new boss, and adds Steam Workshop mod support. The RNG fix came directly off the back of player tckmn's eight-hour video exposé — the patch notes credit them explicitly, saying the team "wouldn't have caught the issue" without it.

The bug centered on Neow's Bones, a starting relic that grants two relics in exchange for a random curse. The problem: the curse wasn't actually random. Players starting in the Underdocks had a 54% chance of receiving the Debt curse, which drains 10 gold every turn you end with it in hand. Mega Crit programmer Ed Lu explained in the changelog that the game uses multiple pseudo-random number generators, each seeded from the main run seed. Those seeds were supposed to be independent, but the decimal values governing which Act 1 you got were correlated with the Neow's Bones curse roll. Lu included two graphs to illustrate the fix — the old PRNG shows clear diagonal lines, the new one looks like white noise with "no human-detectable correlation." He also noted that once an exploit like this is public, players feel compelled to use it, which "is tedious and unfun" — reason enough to patch it fast.

Beyond the RNG fix, the patch replaces the widely-disliked boss Doormaker with a brand-new Act 3 boss called Aeonglass. The update also adds a Bestiary to the Compendium and enables Steam Workshop support for mods — both substantial quality-of-life additions for a game still in early access.

Full patch notes are up on Steam. The tckmn saga is a good reminder that determined players with enough time and a spreadsheet can catch what automated testing misses — and that Mega Crit is clearly paying attention to the community.