Blue Archive: the damage table decides your raid team before you do

Blue Archive resolves damage through a four-by-four table of attack types against armour types. Get the matchup right and you deal double. Get it wrong and you deal half. That is a four-fold swing, and nothing you can do to a student's level, gear or bond comes close to compensating for it.

Which means the first decision in any raid is not "who is strongest" but "who is not halved".

The table

Two things about this table are not obvious from playing:

Explosion is the sharpest and the most punished. It is the only attack type with two 0.5× cells. It doubles against Light and is halved against both Heavy and Elastic. An Explosion-heavy box is excellent against half the content and actively bad against the other half.

Sonic is the flattest. One 2×, no penalties, 1× everywhere else. A Sonic student is never the wrong answer and rarely the best one — a genuinely different risk profile from the other three, and worth remembering when you are deciding what to invest in.

Which boss sits on which armour

Eight raid bosses, and the armour distribution is not even:

Three Heavy, three Special, two Light — and no raid boss uses Elastic armour at all. Sonic's one doubling matchup does not appear in raids.

Against this specific set of eight, Pierce and Mystic each double against three bosses and are halved against three. Explosion doubles against only two and is halved against three. Sonic doubles against none and is halved against none — eight straight 1× matchups.

Read the terrain column alongside it. Terrain applies a separate multiplier through each student's terrain grade, and it is not a small effect: the grade weights run from 1.3× at SS down to 0.7× at E. A perfectly-typed student on bad terrain can be worth less than a neutral one on good terrain.

The roster is not evenly supplied either

Counting students by attack type across the full roster:

Sonic is roughly half as common as anything else — 34 students against 87 Explosion. Combined with the fact that no raid boss carries Elastic armour, a Sonic student is a specialist tool with no raid speciality to be a specialist in. That is a design choice, not an oversight, but it should inform where your resources go.

On the defensive side the roster skews differently again: 87 Light, 87 Heavy, 68 Special, and only 12 Elastic plus 2 Composite. When you are being hit rather than hitting, the armour you are carrying is largely decided for you.

Practical order of operations

1. Check the boss's armour first and eliminate every attack type that is halved against it. This is a larger effect than anything else on the screen.
2. Then check terrain grades on the survivors. An S or SS grade is a 1.2–1.3× multiplier; a D or E is a 0.8–0.7× penalty. That range is wide enough to reorder your shortlist.
3. Then compare stats — and only then. A 20% ATK advantage does not survive a 0.5× type penalty, and it is the last thing that should decide a slot.
4. Do not over-invest in Sonic for raids. Its doubling matchup does not currently appear among the raid bosses.

One limitation to state plainly: this is the type layer only. Skills, cost curves, EX timing and the specific mechanics of each boss all sit on top of it and frequently matter more between two correctly-typed students. What the table settles is which students should be on the shortlist at all — and that is the part players most often get wrong.