Slay the Spire 2 developer shows artwork and concepts for Doormaker boss replacement Aeonglass

Slay the Spire 2 has replaced its Act 3 boss Doormaker with Aeonglass, an hourglass-themed entity that's already one of the game's most visually striking encounters. Developer Mega Crit revealed the design process behind the swap in a recent Steam blog post, showing how the team iterated from a "multi-faceted pillar of death" concept to the final lava-lamp-filled killer hourglass.

Aeonglass is the fourth boss to occupy the Act 3 slot during early access, and it may not be the last. Mega Crit has been aggressively reworking late-game encounters to perfect the roguelike deckbuilder's difficulty curve.

Why This Matters

For anyone who's sunk hours into the original Slay the Spire, boss design is the difference between a run feeling fair and one feeling like a brick wall. An Act 3 boss that's too easy or too unpredictable can sour the entire experience. Mega Crit's willingness to scrap and replace bosses mid-early access shows they're taking the feedback loop seriously.

Animator Chris Gortz explained in the blog post that early concepts for Aeonglass were meant as an upgrade to Doormaker's "rocky portal" design. The team explored a rotating pillar of death before settling on the hourglass motif.

"I did some tests to make sure I could simulate 3D rotating metal rings in 2D space. The result wasn't much to look at, but as a proof of concept it worked well enough for us to move ahead," Gortz wrote.

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From there, doodles led to the idea of "a big atom" with blast and slice attacks. Art director Marlowe Dobbe then requested that the hourglass's contents move "more like lava lamp goo than the traditional sand," pushing Gortz to reuse the smoke shader from the Living Smog boss.

Key Detail

The most recent beta patch has already nerfed Aeonglass's front-loaded damage and swapped some animations. That's a sign Mega Crit is still tuning the fight, even if the visual design is locked in.

Slay the Spire 2 isn't expected to leave early access until 2027 at the earliest, following the original game's 18-month development cycle. Console releases haven't been confirmed but should arrive around the 1.0 launch.

Eurogamer's early access review noted that "Mega Crit demonstrates that it absolutely understands what makes this eccentric card game crackle and fizz." That's a high bar, but the studio's iterative approach to boss design suggests they're willing to keep tweaking until every encounter hits that mark.

For now, Aeonglass stands as a testament to Mega Crit's design philosophy: test, break, test again, and don't be afraid to start over. If you were hoping for a more stable experience, the Steam Deck OLED review might be a better read while you wait for the final product.