Sephiria Unlock Rates: 27 Achievements, 26 Days

This site holds two dated readings of the same Steam statistic: one taken on 12 August 2026, printed in the table on the achievements page, and one taken on 7 September 2026, which the weekly refresh writes into the data file behind the achievement tracker. Twenty-six days apart, same 27 entries, same source endpoint.

Nobody on this site had put the two columns next to each other. That is what this page is. Every number below is one of those two captures or the arithmetic difference between them — nothing here is a new measurement, and no third reading is involved.

All 27, both captures

Rows are in the order of the older capture, so the ordering of the right-hand column is itself a result: where two adjacent rows swap, the ranking changed.

Four things the two columns say

Every single entry rose. Twenty-seven out of 27, no exceptions, not one flat reading. The total movement across the list is 165.5 percentage points, which averages +6.1 per achievement, with a median of +5.2. That is not noise around a fixed value; it is a population statistic climbing in one direction.

The movement is concentrated at the bottom. The ten entries that were most-unlocked in August gained an average of +2.6 points. The ten rarest gained +9.0. DIY, already at 91.7%, could only manage +0.4 because there is almost nothing left above it; Temple of Evil and Journey's End each gained 11.8. A rolling lifetime percentage compresses near 100% and has room to run near the floor, so some of this is arithmetic — but arithmetic does not explain a threefold gap on its own.

The rarest achievement in the game changed hands. On the August capture, Journey's End was the floor of the list at 16.3%, with Seal a tenth of a point above it. By September both sit at 28.1% and the lowest rate in Sephiria belongs to Root's Retreat 30 at 24.2%, which had been three places higher. The three Hard Mode tiers gained +6.8, +6.3 and +4.6 — less than the story tail did — so the population that finished the campaign in late August grew considerably faster than the population grinding stage 30.

One entry refuses to follow its neighbours. Soul Plan sat at 30.8% in August, level with Root's Retreat 15, and gained only +3.6, while the blank-description entries directly below it — Hero's Guise, Temple of Evil, Seal — gained 10.4, 11.8 and 11.7. We have no explanation for that and are not going to invent one; its condition is one of the twelve Steam leaves blank, so there is nothing in the public record to reason from. It is recorded here because a reader comparing an old screenshot to a current one deserves to know which row behaves oddly.

Two pairs that moved in lockstep

Gatekeeper of the Mind and Chapter IV were both on 33.5% in August and are both on 43.1% in September — identical to the tenth of a point across 26 days. Seal and Journey's End, a tenth apart in August, are now exactly equal. Neither pair is evidence of a shared trigger; two achievements earned in the same few minutes of play will track each other closely without being the same event, and the final boss and endings page is where what is actually established about that stretch of the game lives.

What this means for anyone quoting a percentage

A Sephiria unlock rate with no date attached is worth very little. On this evidence the bottom third of the list moves by roughly ten points a month, which is enough to change the answer to "what is the rarest achievement in Sephiria" between one reader's visit and the next. Any wiki, video or forum post that names a rarest achievement without saying when it looked is quoting something that has already expired.

It also means an unlock rate is a poor proxy for difficulty. Journey's End nearly doubled without the game changing: no patch between 1.0.24 and 1.0.30 touched an achievement, so the fight did not get easier, the owner base simply got further into it. A rate measures how many people have reached a thing, and reaching depends on how long the game has been out and who bought it recently — not on how hard the thing is.

How these two readings were taken

Both come from the same Steam endpoint for app 2436940 and cover the same 27 entries, so the comparison is like for like. The August figures were transcribed into the table on the achievements page when it was written; the September figures arrive automatically, refreshed weekly into the site's achievement data file and rendered by the tracker, which is why the tracker prints its own capture date rather than inheriting one from prose.

Both captures are rolling lifetime percentages across all owners — not a sample of active players, not a per-week figure. Valve does not publish the denominator, so a statement such as "76.3% carry the Chapter I marker" is a fact about Steam's stats page and nothing more.

What is not here

No third capture, because this site holds only two. No projection of where any rate will be next month — 26 days of movement between two points is not a trend line, and treating it as one would be a guess dressed up as arithmetic. No conclusion about which boss or chapter is hardest, for the reason given above.

If you are working through the list rather than reading about it, the tracker is the practical version of this page, and the reading order sequences the guides you will want on the way down the ladder.