diff --git a/package.json b/package.json
index c5534bd..a9520af 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,8 @@
     "lint": "oxlint . && eslint . --cache",
     "lint:fix": "oxlint . --fix && eslint . --fix --cache",
     "format": "oxfmt --check src/",
-    "format:fix": "oxfmt src/"
+    "format:fix": "oxfmt src/",
+    "prolog": "swipl src/genealogy.pro"
   },
   "dependencies": {
     "pinia": "^4.0.2",
diff --git a/src/genealogy.pro b/src/genealogy.pro
index cca0cba..d449966 100644
--- a/src/genealogy.pro
+++ b/src/genealogy.pro
@@ -199,6 +199,134 @@ couple(zeus, maia).
 couple(zeus, metis).
 couple(zeus, semele).
 
+% --- figures with no family lines ---
+figure(tartarus).
+figure(eros).
+figure(proteus).
+figure(glaucos).
+figure(scylla).
+figure(argos).
+figure(polydamas).
+figure(alke).
+figure(diomedes).
+figure(palamedes).
+figure(elpenor).
+figure(eurylochos).
+figure(eurycleia).
+
+:- table sibling/2.
 sibling(X, Y) :- parent(P, X), parent(P, Y), X \= Y.
 ancestor(X, Y) :- parent(X, Y).
 ancestor(X, Y) :- parent(X, Z), ancestor(Z, Y).
+
+% ============================================================
+% Generation bands
+% ============================================================
+:- discontiguous band_fixed/2.
+:- discontiguous band_derived/2.
+
+% --- fixed: the primordials (closed set) ---
+band_fixed(chaos, primordial).
+band_fixed(gaia, primordial).
+band_fixed(tartarus, primordial).
+band_fixed(eros, primordial).
+band_fixed(nyx, primordial).
+band_fixed(erebus, primordial).
+band_fixed(uranus, primordial).
+band_fixed(pontus, primordial).
+% the_fury has gaia + uranus as parents - Titan-shaped, but the Erinyes
+% are the old night-dark order.
+band_fixed(the_fury, primordial).
+
+% --- derived bands ---
+% titan: born of gaia and uranus.
+band_derived(X, titan) :-
+    parent(gaia, X),
+    parent(uranus, X).
+
+% olympian
+band_derived(X, olympian) :-
+    parent(kronos, X),
+    parent(rhea, X).
+% the younger ones need an olympian parent plus a second divine one.
+band_derived(X, olympian) :-
+    parent(P, X),
+    band(P, olympian),
+    parent(Q, X),
+    Q \= P,
+    forall(parent(R, X), divine(R)).
+
+% --- fixed: olympians the rules can't reach ---
+% dionysus: mortal mother (semele), but he sits on Olympus.
+band_fixed(dionysus, olympian).
+% aphrodite: single parent (uranus, via the sea-foam).
+band_fixed(aphrodite, olympian).
+% hephaestus: hera alone, no father.
+band_fixed(hephaestus, olympian).
+
+% second_generation: the divine catch-all - Helios's line, the oceanids,
+% atlas/prometheus, the sea line.
+band_derived(X, second_generation) :-
+    parent(P, X),
+    parent(Q, X),
+    P @< Q,
+    divine(P),
+    divine(Q),
+    \+ band_derived(X, titan),
+    \+ band_derived(X, olympian).
+
+% astraios: only crius recorded (eurybia isn't in the file).
+band_fixed(astraios, second_generation).
+% neaera: parentless nymph, mother of lampetia and phaethousa by helios.
+band_fixed(neaera, second_generation).
+% proteus: the old man of the sea, no family lines recorded.
+band_fixed(proteus, second_generation).
+
+% --- fixed: heroes & legends ---
+% hero = a mortal with their own story cycle.
+band_fixed(heracles, hero).
+band_fixed(theseus, hero).
+band_fixed(jason, hero).
+band_fixed(achilles, hero).
+band_fixed(odysseus, hero).
+band_fixed(medea, hero).
+band_fixed(daedalus, hero).
+
+% --- divine: used by the derived rules above ---
+divine_band(primordial).
+divine_band(titan).
+divine_band(olympian).
+divine_band(second_generation).
+
+divine(X) :- band(X, B), divine_band(B).
+
+% --- the bridge: rulings always win ---
+:- table band/2.
+
+band(X, B) :- band_fixed(X, B).
+band(X, B) :- band_derived(X, B), \+ band_fixed(X, _).
+band(X, mortal) :-
+    known_figure(X),
+    \+ band_fixed(X, _),
+    \+ band_derived(X, _).
+
+% --- audits: run after every change ---
+mentioned(X) :- figure(X).
+mentioned(X) :- parent(X, _).
+mentioned(X) :- parent(_, X).
+mentioned(X) :- couple(X, _).
+mentioned(X) :- couple(_, X).
+
+known_figure(X) :- distinct(X, mentioned(X)).
+
+% a known figure no band claims
+unbanded(X) :- known_figure(X), \+ band(X, _).
+
+% a figure claimed by two different bands
+bands_of(X, Bs) :- setof(B, band(X, B), Bs).
+overbanded(X) :- known_figure(X), bands_of(X, Bs), Bs = [_, _ | _].
+
+% a ruling naming a figure no other fact knows
+phantom_ruling(X) :- band_fixed(X, _), \+ known_figure(X).
+
+band_count(B, N) :- setof(X, band(X, B), Xs), length(Xs, N).